CLASS IV 



GASTROPODA 



549 



tuith short canal or shallow notch. Columella and lips with strong folds, continuous 

 throughout the entire length of the spire. Outer lip thin, posteriorly with fissure-like 

 incision, which leaves a small slit-hand immediately beneath the suture on all the ivhorls. 

 Marine. Trias to Cretaceous. 



Aptyxiella Fisch. (Aptyxis Zitte], non Troscliel). Turreted, very slender, im- 

 perforate. Aperture quadrangular ; inner and outer lips without folds ; columella 

 somewhat thickened. Trias to Upper Jura. 



Trochalia Sharpe {Gryptoplocus Pict. and Camp.) (Fig. 972). Turreted to 

 pyramidal, usually smooth and imperforate. The inner lip only has a strong, simple 

 fold. Jura and Cretaceous. 



Nerinella Sharpe (Pseudonerinea Loriol). Turreted, imperforate. Outer lip and 

 sometimes also the columella with a simple fold. Jura. 



Nerinea Defr, (Fig. 973). Turreted or pyramidal, usually imperforate. Columella 

 invariably, and inner and outer lips generally, with simple folds. Jura and Cretaceous ; 

 maximum in the Coral-Rag (Upper Jura). 



Ptygmatis Sharpe (Fig. 974). Like the last, except that the folds on both lips 

 and the columella are complicated by second- 

 ary constrictions and branchings. Jura and 

 Cretaceous. 



Itieria Math. (Fig. 975). Elongate-oval, 

 usually umbilicate. Spire short, sometimes 

 insunken. Body whorl very large, more or 

 less enveloping the preceding. Columella 

 and both lips with folds. Jura and Cre- 

 taceous. 



Family 17. Oerithiidae Menke. 



Shell turreted; aperture elongated oval, or 

 quadrilateral, anteriorly ivith short canal. 

 Outer lip often thickened and reflected, or thin 

 and sharp. Columella sometimes with one 

 or two folds. Operculum horny, spiral. 

 Marine and brackish ivater. Trias to Recent. 



Fio. 974. 



Ptygmatis pscndo- 

 linndrutana Gem- 

 mellaro. Titlionian ; 

 Iiiwald, Carpathia. 

 Vertical section. 



Fig. 975. 



Itieria staszycii Zeuschner. 

 Tithonian ; Inwald, Car- 

 pathia. 



The earliest 



More than 1000 living, and about 500 

 fossil species are known, the latter being most numerous in the Eocene, 

 forms ai-e usually of small size, and have a nearly entire peristome. 



Cerithinella Gemm. (Fig. 976). Shell turreted, slender. Whorls numerous, flat, 



ornamented with spiral ribs or rows of small nodes. 

 Aperture c^uadrilateral, 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 



Pio. 977. 



Fia. 976. 



Cerithinella armata 

 Goldf. Torulosus 

 Beds (.Middle Jura) ; 

 Pretzfeld, Franconia. 



Mordf and Tyc' quadrilateral, with scarcely perceptible canal. 



Great Oolite ; Min- rj,j.-j^g ^^^ j^^^,^ 



chinhanipton, Jing- ^ . ,, ,, . -it ,tt n^,^~^ m • 



land. Ceritella Morris and Lye. (Fig. 977). Trias 



and Jura. Fibula Piette (Fig. 978). Trias to 

 Cretaceous. Pseudalaria Huddlest. ; Ditretus Piette. Jura. 



Exelissa Piette (Fig. 979). Very small, turreted ; whorls with strong, continuous 



