SUB-ORDER B 



I'LATVI'ODA 



ha MT. 



CerithliH'llii unit'ito, 

 Goldf. Torulosus 



FN.. 928. 



Morris ami I.\ <. 

 Cn-at oulit- : Miii- 

 fhinhainptoii. 



land. 



Cerithinella, Oemin. (Fig. 927). Shell turreted, slender. \Vln.i]- nuiiit-roii.-, Hat. 

 ornamented with spiral ribs or rows of small node<. 

 Aperture quadrilateral, with very faint canal. Jura. 

 Cryptaulax, Tate (Pseudocerithiurn, ( 'n.-.-iiiaiin . 

 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 

 quadrila.teral,'with scarcely percep- 

 tible canal. Trias and Jura. 



Ceritella, Morris and Lye. (Fig. 

 1)28) ; Trias and Jura, Fibula, 



Piette (Fig. 929) ; Trias to Cretaceous. Pseudalaria, Huddli-M. : 



Ditretus, Piette ; Jura. 



Exelissa, Piette (Fig. 930). A'. ry 

 small, turreted ; whorls with strong, 

 continuous transverse ribs and spiral 

 striae. Aperture contracted, 

 rounded, without canal, sometim.-.- 

 slightly separated off, and with 

 continuous peristome. Abundant 



Fm. 931. i n t ] ie J ura- 



Bittium plicatum Bittium, Leach (Fig. 931). Tur- 



Brug. Oligocene; -, . , ., 



Ormoy, near Etampes, reted, with granulated spiral ribs, and 



France - numerous trans verse 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. 



Fio. 929. 



Fibula undulosa, 

 Piette. Bathon- 

 ian ; Eparcy, 

 Aisne. 



FK;. 930. 



Exelissa strangu- 

 lata, d'Arch. sp. 

 Bathonian ; 

 Eparcy, Aisne. 



FIG. 932. 



Cerithium sermtum, 

 Brug. CalcaireGrossier; 

 Dainery, near Epernay. 



FIG. 



Cerithium, (Vertagus) 

 7ii{u?n, Lani. Eocene; 

 Chaumont, near I'aris. 



Fio. 934. 



Potamides (Tympana- 

 torn *) margaritaceum, 

 Brocchi. Oligocene; 

 Hackenheim, near Alzey. 



Fio. 935. 

 Potamides (I.i' 

 pli'iiri'tmnoiiJes, Desh. 

 Middle Meert'ssand ; 

 Mortefontaine, Seine- 

 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. giganteum). Jura to Recent ; maximum in Eocene. 

 Sub-genera : Vicarya, d'Arch. ; Vertagiis, Klein (Fig. 933) ; Bellardia, Mayer, etc. 



Potamides, Brongt. (Figs. 934, 935). Turreted, with epidermis ; aperture with 



