EGG—Conoidal, truncated, not so broad at base as Idalia, the sides less rounded ; depressed at summit; marked vertically by about eighteen prominent, slightly wavy ribs, half of which extend from base to summit and form around the latter a serrated rim; the remainder end irregularly at two thirds to three quarters distance from base, sometimes squarely at one of the striæ, but usually curve towards and unite with the long ribs; between each pair of ribs are equi-distant transverse striæ.