CLASS IV 



GASTROPODA 



525 



Pohjtremaria de Kon. Shell turbinate, with band replaced l)y a row of perfora- 

 tions, of which the posterior ones are siiccessively closed. Carboniferoiis. 



Düremaria d'Orb. (Fig. 855). Two oval pefforations connected by a slit are 

 present beliind the outer lip ; base with an umbilical callus. Jura. 



Trochotoma Deslongch. Shell turbin- a b c 



ate, with conical base. A slit closed at 

 either end is present behind the outer 

 lip, and corresponding to it is a slit-band. 

 Trias and Jura. 



Fig. 855. 



Ditremaria granulifera Zittel. Upper Tithonian 

 Stramberg, Moravia. 



Fig. 856. 



A, MurcMsonia Mlincata d'Arch. and Vern. 

 Devonian ; Paflfrath, near Cologne. B, M. hlumi 

 Klipstein. Trias ; St. Cassian, Tyrol. C, M. 

 siibsulcata de Kon. Lower Carboniferous ; Tour- 

 nay, Belgium. Last two whorls, 2/j. 



Schizogonium Koken ; l'emnotropis Laube ; Gantantostoma Sandb. Devonian. 



MurcMsonia d'Arch and Vern. (Fig. 856). Shell turreted, with numerous smooth 

 or ornamented whorls Outer lip with a slit, and corresponding to it a slit-band. 

 Cambrian to Trias. Maximum distribution in Devonian and Carboniferous. 



Lophospira Whitf. (Fig. 857, Ä, ß). Shell with more or less elevated spire ; 

 whorls angular on the periphery and bearing from one to five distinct carinae. 

 Ordovician to Devonian. 



Hormotoma Salter (Fig. 857, D). Elongate, beaded, practically imperforate ; outer 

 lip with broad, deep notch. Ordovician and Silurian. 



Liospira Ulr. and Scof. Shell lenticular with aperture deeply notched and 

 band scarcely distinguishable. Ordovician and Silurian. 



Schizolopha and Turritoma Ulrich. Oidovician and Silurian. Seelya,' Plethospira 



A B CD 



Fi(i. 857. 



A, B, Lopliospira sumnereiisis (Safford). Ordovician ; Tennessee. C, Trepospira spheriüata (Conrad). Goal 

 Measures ; Illinois. D, Hormotoma salteri Ulrich. Ordovician ; Kentucky. 



and Euconia Ulrich. Ordovician. Goelocaulus (Ehlert ;• Clathrospira Ulr. and Scof. ; 

 Ectomaria Koken {Solenospira Ulr. and Scof.). Ordovician and Silurian. Bemhexia 

 (Ehlert ; Trepospira Ulr. and Scof. (Fig. 857, G). Devonian and Carboniferous. 



Family 3. Fissurellidae Risso. 



Shell symmetricaly cap- or limpet-shaped, non-nacreous^ without operculum. Apex 

 erect or pointing hackward, often recurved, perforated. Anterior margin often with a 

 fissure ; yoimg shell with a spiral protoconch. Marine ; shore forms. Carboniferous to 

 Recent. 



