During the Cretaceous Period, gastropod faunas show considerable differences in their evolution between the Tethyan Realm (tropical) and the Temperate Realms to the north and south. Like Holocene faunas, prosobranch gastropods constitute the dominant part of Cretaceous marine snail faunas. Entomotaeneata and opisthobranchs usually form all of the remainder. In Tethyan faunas the Archaeogastropoda form a consistent high proportion of total taxa but less than the Mesogastropoda throughout the period. In contrast, the Temperate faunas beginning in Albian times show a decline in percentages of archaeogastropod taxa and a significant increase in the Neogastropoda, until they constitute over 50 percent of the taxa in some faunas. The neogastropods never attain high diversity in the Cretaceous of the Tethyan Realm and are judged to be of Temperate Realm origin.

Cretaceous Tethyan gastropod faunas are closely allied to those of the “corallien fades” of the Jurassic and begin the period evolutionarily mature and well diversified. Greatest diversity in Tethys occurs in the lagoonal shales associated with the rudist or coral framework environments of the Cretaceous carbonate platforms. Their distribution was pan-tropical, extending in instances across the vast reaches of the Pacific. Three categories of Tethyan gastropods are analyzed. The first group consists of those of Jurassic ancestry. Except for the Nerineacea, these taxa are long ranging but evolutionarily conservative, showing only moderate diversification during the Cretaceous, and becoming extinct with the close of the era. The second group originates mainly during the Barremian and Aptian, reaches a climax in diversification during middle Cretaceous time, and usually declines during the latest Cretaceous, with most not lasting through the terminal event. The third group originates late in the Cretaceous and consists of taxa that manage to either survive the Cretaceous-Tertiary crisis or give rise to forms of prominence among Tertiary warm water faunas.

There is a trend among the Tethyan gastropod assemblages for increased provincialism with time. Early and middle Cretaceous taxa are especially widely distributed, but the latest Cretaceous is a time of restricted occurrence for many forms.

Temperate Realm gastropod faunas are less diverse than those of Tethys during the Early Cretaceous. Their source is among long lived, extra-Tethys groups, but is increased, especially during major phases of transgression, by immigrants from Tethys. They show a steady increase in diversity, primarily among the Mesogastropoda and Neogastropoda. This trend culminates in latest Cretaceous times when the gastropod assemblages of the clastic provinces of the inner shelf contain an abundance of taxa outstripping that of any other part of the Cretaceous of either realm.

Extinction at the Cretaceous-Tertiary boundary is much less pronounced in the Temperate Realm than in the Tethys. Among the Temperate Realm assemblages loss is of generic and species level taxa, unlike the extinction of the family Actaeonellidae or the superfamily Nerineacea and a host of less prominent groups in Tethys. In essence, by the late Maastrichtian, gastropod faunas of the Temperate Realm had attained a modern faunal aspect.

Two forms of branched, thickly walled, meniscate trace fossils occur in the Permian of East Greenland and Miocene of southern Italy. A new ichnogenus, Rutichnus, is erected for these specimens, and its possible synonyms and mode of formation are discussed. The two ichnospecies, R. irregularis (D'Alessandro) and R. rutis n. ichnosp., differ in the manner of branching and external rugosity.

Detailed morphological study of well-preserved specimens of Bukryaster hayi (Bukry) Prins and Sissingh by means of light and scanning electron microscopes reveals that the arms of the star-shaped nannofossil are pierced by pronounced perforations, reminiscent of those of the Tertiary genus Pemma Klumpp. Those and other features differentiate the taxon from Rucinolithus hayii Stover (1966) and help delimit the stratigraphic range of this important Campanian nannofossil.

A large collection of Silurian halysitids, mainly from the Limestone Point, La Vieille, and Petit Rocher Formations of northern New Brunswick, includes nine species distributed among Catenipora Lamarck, Halysites Fischer von Waldheim, and Cystihalysites Tchernyshev. One species, Cystihalysites belledunensis, is new, and, of the others, half are previously unknown in the Chaleur Bay region and half have been described before from this area.

All species are defined using both qualitative and quantitative data. Statistical analysis of serial sections of a corallum of Cystihalysites belledunensis suggests that any random section of a halysitid will yield quantitative data representative of that colony.

Preliminary analysis of the relationships between species distributions and stratigraphy and sedimentary associations suggests strong facies-control on the distribution of the four most abundant species. Both Catenipora simplex (Lambe) and Catenipora micropora (Whitfield) occur mostly in outer shelf facies. Cystihalysites belledunensis n. sp. and Cystihalysites encrustans (Buehler) never occur together, the former being found in predominantly high-energy inner shelf facies and the latter in the outer shelf facies.

Examination of collections from the Falkland Islands and South Africa shows that Chonetes falklandicus Morris and Sharpe, 1846, is a true Chonetes and is probably conspecific with Chonetes (Pleurochonetes) lauriata Isaacson, 1977, from Bolivia. Notiochonetes skottsbergi (Clarke, 1913) is quite different from C. falklandicus but is often associated with it in Malvinokaffric Realm Lower Devonian deposits.

Septirhynchia hirschi n. sp. is described from the Callovian (Jurassic) strata of Gebel El-Maghara, northern Sinai, Egypt. Significant ontogenetic changes from juvenile to adult include: 1) increase in height of the ventral median septum; 2) change from hypothyridid to mesothyridid pedicle foramen; 3) change from a pyriform to a gibbous outline; 4) change from a weakly defined to a strongly defined pedicle sulcus; and 5) change from a relatively straight to a strongly arched lateral commissure. All ontogenetic stages, except for neanic, possessed a pedicle tube. Muscle scars (diductor) were observed for the first time in the genus on several pedicle valve interiors; none were noted on any brachial valve interiors. Juveniles lived epifaunally, attached to the substrate by a small but functional pedicle, while adults lived semi-infaunally with the umbos buried in the mud.

Collection of over a dozen specimens of Hyolithes aclis Hall from the Middle Devonian of New York indicates that this species belongs to a new genus, Hallotheca, to which the species Hyolithes halli (Hall) is also assigned. However, the generic assignments of the Silurian species Hyolithes cliftonensis Foerste and the Devonian species H. centennialis Barrett, H. ceratophilus Clarke, H. neapolis Clarke, and H. triliratus Hall are uncertain because of poor preservation of their type specimens. Use of these names should be confined to the types until better preserved topotypes become available. Finally, H. cooperi (Williams) consists of organisms of uncertain affinities, and the type of H. principalis Hall may be a fragment of Devonian sandstone rather than an organism.

Pharkidonotus megalius n. sp. is described from the Desmoinesian of the Mud Springs Mountains, New Mexico. This unusually large bellerophontid reaches a length of at least 90 mm and is also characterized by a prominent high median ridge bearing a narrow selenizone and subdued collabral ornamentation on the whorl surface at all stages of growth. Its size and subdued ornamentation are quite different from that of the two previously known North American Pennsylvanian species of Pharkidonotus. Although steinkerns of comparable size have been reported from several localities in North America, the specimens discussed here are the first relatively well preserved shells of very large Pennsylvanian bellerophontids to be described.

Examination, utilizing scanning electron microscopy, of 58 specimens of Hoploparia stokesi (Weller) from the Maastrichtian portion of the Lopez de Bertodano Formation, Seymour Island, Antarctica, leads to the conclusion that cuticular ultrastructure may be used to distinguish molted from deceased remains of nephropid lobsters. Molted cuticle is characterized by deterioration, or loss, of lamination in the inner endocuticle whereas cuticle, during the intermolt phase, exhibits lamination throughout the endocuticle as well as the exocuticle. Diagenetic effects may obscure lamination throughout the cuticle. These observations confirm that Salter's position is typical of molted remains in fossils. Furthermore, partial remains of H. stokesi generally are molts. Preservational quality of molted remains tends to be better than that of corpses.

The Florena Shale (Permian, Wolfcampian) of the Midcontinent of North America was deposited in a restricted marine basin. Shifting environments due to marine regression caused a gradual change in the ostracode fauna. Cluster analysis and ordination by nonmetric multidimensional scaling of data on ostracode relative abundances revealed three ostracode assemblages, each characteristic of a different environment. The Cryptobairdia seminalis assemblage from the lowest Florena Shale is characteristic of deeper water, offshore, marine environments with only minor influx of terrigenous mud. The Amphissites centronotus assemblage found above the C. seminalis assemblage occupied a similar environment, but with greater influx of terrigenous mud and intervals of increased turbidity. The Knightina texana assemblage occurs stratigraphically highest and probably represents a quiet-water, very shallow, nearshore, marine environment. Although protected from strong wave and current activity, the water mass was occasionally turbid.

Species diversity of ostracodes is high both at the base of the Florena Shale, which was deposited in the most offshore position, and again at the top of the lower part of the Florena Shale, which was deposited nearer to the shore. In contrast to diversities of assemblages of ostracodes from similar environments in other stratigraphic units, the K. texana assemblage has an anomalously high diversity. This is due in part to time averaging of adjacent ostracode assemblages and a strong taphonomic overprint.

Closterocrinus elongatus Hall, 1852, long assigned to the cladid inadunate crinoid family Ampheristocrinidae (=Euspirocrinidae), has been found to possess pinnulate biserial arms and a cup composed of four exsert basals, five radials, a primanal above the radial circlet, and fixed primibrachials and secundibrachials. Accordingly, this species is herein reassigned to the monobathrid camerate crinoid family Paramelocrinidae.

Mandalacystis dockeryi n. gen. and sp. is known from seven complete or nearly complete thecae, six partial thecae, and numerous separate plates from the Oil Creek Formation in south-central Oklahoma, and a single thecal plate from the Antelope Valley Limestone in Nevada. Details of skeletal microstructure (stereom) are well preserved, permitting scanning electron microscopy for the first time in the Eocrinoidea, and demonstrating that plate thickness on thecal faces is only 60–70 μm. Mandalacystis is characterized by labyrinthine ridges on both faces of the theca, relatively short brachioles, and a normal stem with holdfast (at least in juvenile stages). Based on the normal biserial arrangement of brachiolar plates in the brachioles and the possession of a normal stem, Mandalacystis appears to be one of the most primitive rhipidocystids, closely related to Petalocystites.

Mandalacystis dockeryi lived in a storm-dominated, shallow-water offshore habitat on patches of skeletal debris surrounded by soft, terrigenous mud. This setting may have been conducive to the transition from an erect, attached mode of life to the prone, unattached lifestyle of later rhipidocystids.

A method has been developed that uses holographic interferometry to generate contour maps of the occlusional surfaces of fossil teeth. The resulting contour map is, in itself, a valuable descriptive tool. In addition, it provides information for a very large data base, which has been used in trend-surface analysis and Q-mode clustering. As an example, these analytical techniques are applied to a set of Pliocene badger teeth. The same methods can be applied to any paleontological problem dealing with shapes of small objects.

Additional information on the alleged gastroliths in Early Cretaceous formations of the Western Interior has changed the writer's opinion from skepticism about a dinosaur causative agency to belief that it is a valid explanation. Concentrations of exotic rounded and polished stones have been found in close association with a number of skeletons. Aside from this, the best evidence is distribution of individual stones in environments where inorganic agencies seem improbable; distinctive individual stones have apparently been carried hundreds of kilometers. Gastroliths have value as quasi-guide fossils. From geographic and geologic associations it is suggested that various sauropods and perhaps the contemporary ornithopod, Tenontosaurus tilleti, were the chief stoneswallowers of the Early Cretaceous of the Western Interior.

Upper dentition of Protosciurus mengi Black, from the Orellan Brule Formation, Nebraska, is described for the first time. The zygomatic plate is tilted anterodorsally, showing the beginnings of sciuromorphy as in the Arikareean species of this genus. A new genus of sciurid, Oligospermophilus, is named for the species originally identified as ?Protosciurus douglassi (Korth), based on additional material including a skull and upper dentitions. The zygomasseteric structure of O. douglassi is unlike any previously described Tertiary sciurid. The range of O. douglassi is extended from the late Chadronian to the Whitneyan. Three distinct lineages of sciurids, distinguished on dental morphology and zygomasseteric structure, can be traced in the Oligocene in North America; they are represented by the genera Protosciurus, Oligospermophilus, and ?Protosciurus.

African machairodont specimens previously referred to three species of Megantereon are considered to represent a single species in turn argued to be conspecific with the Eurasian species Megantereon cultridens (Cuvier). The area of origin of Megantereon remains unclear, but doubt is expressed about claims for an earliest appearance of the genus in North America. It is probable that the North American species M. hesperus is a junior synonym of M. cultridens.