On comparing the figures it will be observed that all the specific characters of Tetrophthalmus titan (A in all figures) closely resemble those of T. subtitan (B in all figures), and that these two species constitute one group; also that the specific characters of T. africanus (C in all figures) closely resemble those of T. australis (D in all figures), and that these species belong to another group, which must also include T. chilensis.

Judged by their parasites, the Ethiopian pelican, Neopelecanus rufescens, is more closely allied to both the Australian pelican, Catoptropelecanus conspicilatus, and the South American species, Pelecanus thagus, than it is to either Pelecanus onocrotalus or Metapelecanus roseus, both of which also occur in the Ethiopian region. Moreover, if the parasites throw any light on the phylogeny of their hosts, thagus cannot remain in the genus Pelecanus along with onocrotalus if the genera Neopelecanus, Metapelecanus and Catoptropelecanus are to remain valid.