346 GASTEROPODA OF THE INFERIOR OOLITE. 



Crossostoma discoideum. and C. heliciforme, which he finally regarded as adult and 

 discoidal forms of smooth " Monodontas," leaving only Crossostoma Prattii as the 

 representative of the genus. This fossil was said to have come from the Inferior 

 Oolite near Bath. I have not succeeded in obtaining a sight of the type. The 

 genus is held to include Crossostoma (Delphinula) reflexilabrum, d'Orb., from the 

 Lias. 



280. Crossostoma, sp. ; cf. Crossostoma Prattii, Morris and Lycett, 1851. Plate 



XXVIII, figs. 17 ft, 17 b. 



1851. Crossostoma Prattii, Morris and Lycett. Great Ool. Moll., pt. 1, p. 72, 



pi. xi, figs. 21, 21a. 

 Cf. also Rotella macrostoma, Stoliczka. Hierlatzschicten, p. 178, pi. iii, fig. 5. 



Teinostoma Neumatri, Genvmellaro. Faune G-iuresi, &c, p. 344, pi. xxvii, 



figs. 15, 16. 



Description. — Shell thick, nearly twice as wide as high, discoidal ; spire greatly 

 depressed. The width of the figured specimen is 15 mm., and of a smaller one, 

 which I possess, 10 mm. The body-whorl is essentially rotelliform, the aperture 

 small and circular, and there is a considerable thickening towards the columellar 

 extremity. 



N.B. — There is no umbilicus, as might possibly be inferred from the figure. 



Relations and Distribution. — The probable relations of this very discoidal shell 

 are indicated in the list of references. It may be Crossostoma Prattii, but if so the 

 figure in the ' Great Oolite Mollusca ' is not sufficiently discoidal. The form is 

 very rare. The figured specimen is a brown ferruginated fossil, suggestive of 

 Dundry or of some of the Dorset beds. Another specimen in my collection is 

 from the Pea-grit of Crickley. This is much smaller, and altogether more repre- 

 sentative of C. Prattii, as far as one can judge of that species. 



Genus— Ataphrus, Gabb, 1869. 



The bulk of the smooth "Monodontas" remain to be described, and the 

 question for consideration is — under what genus ? Monsieur Cossmann, in his 

 excellent memoir on the ' Bathonian ' in France, adopted the genus Ataphrus. He 

 attached much importance to the presence of a columellar furrow in the species 

 thus classified by him. Certainly, in the majority of the smooth " Monodontas " 



