CLASS rv 



GASTROPODA 



525 



Polytremaria de Kon. Shell turbinate, with band replaced by a row of perfora- 

 tions, of which the jjosterior ones are successively closed. Carboniferous. 



Ditremaria d'Orb. (Fig. 855). Two oval perforations connected by a slit are 

 2)resent behind 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. 



Fl(,i. 855. 



Ditremaria granuUfera Zittel. Upper Tithonian ; 

 Stramberg, Moravia. 



Fig. 856. 



A, Murchisonia bilineata d'Arch. and Vern. 

 Devonian ; Paffrath, near Cologne. B, M. hlinni 

 Klipstein. Trias ; St. Ca.ssian, Tyrol. C, M. 

 subsulcata de Kon. Lower Carboniferous; Tour- 

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



Schizocjonium Koken ; Temnotroins Laube ; Gantantostoma Sandb. Devonian. 



Murchisonia 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. 



Loi^liospira Whitf. (Fig. 857, A, B). Shell with more or less elevated spire ; 

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

 Ordovieian to Devonian. 



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

 lip with broad, deep notch. Ordovieian and Silurian. 



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

 band scarcely distinguishable. Ordovieian and Silurian. 



Schizolopha and Turritoma Ulrich. Ordovieian and Silurian. Seelya, Plethospira 

 A n c D 



Pig. 857. 



A, B, Loplwspira sumnerensis (Safford). Ovdovician ; Tenne.ssee. C, Trepospira spherulata (Conrad). Coal 

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



and Euconia Ulrich. Ordovieian. Coelocauhis CEhlert ; Clathrospira Ulr. and Scof. ; 

 Ectomaria Koken [Solenospira Ulr. and Scof). Ordovieian and Silurian. Bemhexia 

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



Family 3. Fissurellidae Risso. 



Shell symmetrical, cap- or limpet-shaped, non-nacreous, ivithout operculum. Apex 

 erect or pointing hachward, often recurved, perforated. Anterior margin often ivith a 

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

 Recent. 



