SUB-ORDER B PLATYPODA 469 
Cerithinella, Gemm. (Fig. 927). Shell turreted, slender. Whorls numerous, flat, 
ornamented with spiral ribs or rows of small nodes. 
Aperture quadrilateral, with very faint canal. Jura. 
Cryptaulax, Tate (Pseudocerithium, Cossmann). 
Small, turreted. Whorls with spiral ribs or rows 
of nodes and transverse folds. These last usually 
run continuously in a somewhat oblique direction 

from one whorl to the next. Aperture oval or Fic. 928. 
. . d x O97 
quadrilateral, with scarcely percep- igen Ceritella —conica, 
: : Cerithinella armata, Morris and Lye. 
tible canal. Trias and Jura. Goldf. Torulosus Great Oolite ; Min- 
Ceritella, Morris and Lye. (Fig. ie il Jura) ; cheney Eng- 
928); Trias and Jura. Fibula, = ° anti 
Piette (Fig. 929); Trias to Cretaceous.  Pseudalaria, Huddlest. ; 
Ditretus, Piette; Jura. 
Exelissa, Piette (Fig. 930). Very 
small, turreted ; whorls with strong, 
continuous transverse ribs and spiral 
striae. Aperture contracted, 
rounded, without canal, sometimes 
slightly separated off, and with 
continuous peristome. Abundant 

Fic. 929. Fic. 930. Fic. 931. in the Jura. 
Fibula undulosa, Exelissa strangu- Bittium plicatum pepe? x . a 
Piette. Bathon- lata, dArch. sp. Brug. Oligocene; Bittrwm, Leach (Fig. 931). Tur 
ian; Eparcy, Bathonian; Ormoy, near Etampes, reted, with granulated spiral ribs, and 
Aisne. Eparcy, Aisne. France. . 
numerous transverse costae. Aperture 
with short, straight canal; outer lip sharp. Jura to Recent. Abundant in the Tertiary. 
Triforis, Deshayes ; Cerithiopsis, Forbes. Tertiary and Recent. 
Eustoma, Piette. Aperture with long canal, which is often 
closed, however, by margins of the inner and outer lip. Inner lip 
callous and strongly 
dilated ; outer lip ex- 
panded. Jura. 

Fic. 935. 
Fic. 934 . F 
tee Potamides (Lampania) 
MG. 932 . 933. ; 74 a. 
eee: He 205 Potamides (Tympano- pleurotomoides, Desh. 
Cerithium — serratum, Cerithium (Vertagus) tomus)  margaritaceum, Middle Meeressand ; 
Brug. Calcaire Grossier; nudum, Lam. Eocene ; Brocchi. Oligocene; Mortefontaine, Seine- 
Damery, near Epernay. Chaumont, near Paris. Hackenheim, near Alzey. et-Oise. 
Cerithium, Brug. (Figs. 932, 933). Turreted, imperforate, without epidermis. 
Aperture oblong, ovate, with backwardly curved canal; outer lip often somewhat re- 
flected. Columella concave, frequently with one or two folds. Certain Tertiary species 
attain a length of half a meter (C. giganteuwm). Jura to Recent ; maximum in Eocene. 
Sub-genera: Vicarya, d’ Arch. ; Vertagus, Klein (Fig. 933) ; Bellardia, Mayer, ete. 
Potamides, Brongt. (Figs. 934, 935). Turreted, with epidermis; aperture with 
