THE GASTROPODA 



147 



obtained in 1871, in a collection made off the Barbadoes by the 

 " Hassler" (A. Agassiz). The Moluccan species is nineteen centimetres 

 in height. The genus includes several hundred extinct species, ranging 

 from the Silurian to the Tertiary, but is rare in the last named. 

 Xdssurella, d'Orbigny ; epipodium with tentacles ; right ctenidium mono- 

 pectinate (Fig. 128). Schismope, Jeffreys ; the slit at the margin of 

 the shell is closed in the adult and transformed into an orifice (Fig. 62). 

 The following genera are exclusively fossil : Porcellia, LeVeiHe" ; Devonian 

 and Carboniferous. Kokenella, Kittl ; Trias. Ditremaria, d'Orbigny ; 

 Jurassic. Polytremaria, de Koninck ; Carboniferous. Trochotoma, 

 Deslongchamps ; Trias and Jurassic. Cantantostoma, Sandberger ; 



FIG. 127. 



Flcitrotomaria, with the pallial cavity laid open, right-side view, o, anus ; CM, aorta ; a.v, 

 afferent branchial vessel ; br.g, branchial ganglion ; c.c, cerebral commissure ; co, columellar 

 muscle ; tr, crop ; e.v, efferent branchial vessel ; /, foot ; g, right or minor gill ; g.d, genital 

 duct ; gg, gonad ; h, heart in the pericardium ; hy.g, hypobranchial gland ; in, intestine ; li, 

 liver; l.k.o, opening of the left kidney; m, mouth; m.s, mantle slit; od, odontophore ; oc, 

 oesophagus ; op, operculum ; os. osph radium ; pe.c, pedal cord ; r, rectum ; r.k, right kidney ; 

 r. A', anterior part of ditto (dotted line); r.k.o, opening of the right kidney ; r.,, radularsac; s.g, 

 salivary gland ; sp.c, spiral caecum ; st, stomach. (After F. M. Woodward.) 



Devonian. Muirhisonia, d'Archiac and Verneuil ; Cambrian to Trias. 

 Odontomaria, Roemer ; Devonian. FAMILY 2. BELLEROPHONTIDAE, Mac- 

 Coy. An exclusively fossil family, comprising more than 300 

 species extending from the Cambrian to the Trias. The shell is coiled 

 in one plane and has an incision in the mid -dorsal margin of the 

 aperture. Genera Bellerophcn, Montfort. Euphemus, MacCoy. Salpingo- 

 stoma, Roemer. Trematonotus, Hall. Cyrtolites, Conrad. FAMILY 3. 

 EUOMPHALIDAE, de Koninck. Also an extinct family, extending from 

 the Cambrian to the Cretaceous. Spire slightly prominent ; umbilicus 

 deep ; operculum calcareous. Genera Euomphalus, Sowerby. Strapa- 

 rollina, Billings. Ophileta, Vanuxem. Maclurea, Lesueur. Platychisma, 

 MacCoy. Straparollus, Montfort. Phanerotinus, Sowerby. Discohelix, 



