CERITHIUM. 173 



Sowerbyi-bed at Bradford Abbas, and the variety C occurs on what is nearly the 

 same horizon at Beaminster. It has occurred to me that possibly Gerithium 

 Lorieri, D'Orb. (Prod., i, 271), from the Bajocian of the Sarthe might in some 

 sense represent this species. 



102. Cerithium polystrophum, sp. nov. Plate X, figs. 12, 13. 



Description : 



Length (estimated) . . .55 mm. 



"Width . . . . 105 mm. 



Spiral angle . . . .14°. 



This species so nearly approaches Gerithium abbas, var. B, that it is best 

 described by comparison with that form. The shell is more uniformly subulate, 

 having a narrower spiral angle ; the whorls are all convex, the principal convexity 

 being rather below the middle ; there is no trace of a shoulder in any of them. 

 The spiral strise are very close, regular, and equal. In the earlier whorls (fig. 13) 

 the ornaments consist of about half-a-dozen such strias, those adjoining the sutures 

 being slightly crenulate ; in the mature whorls these lines increase in numbers till 

 they are not far short of twenty. 



The body-whorl is rather short in comparison with the entire shell ; aperture 

 ovate- elongate, with a well-developed anterior canal. 



Relations and Distribution. — This fossil is rare in the Lincolnshire Limestone 

 of Weldon. The condition of the few specimens is by no means satisfactory, so 

 that its actual relations to G. abbas cannot be fully made out. 



103. Cerithium obornense, sp. nov. Plate X, fig. 11. 



Description : 



Length (restored) . . .60 mm. 



Width . . . .12 mm. 



Spiral angle . . . .15°. 



Shell elongate, somewhat turrited ; spiral angle regular. Whorls numerous, 

 flat, and sub-concave, much broader than high, and slightly rising towards the 

 sutures, which are bounded on either side by a raised rim, of which that on the 

 lower side is the strongest. The ornaments consist of numerous fine spiral 

 lines of somewhat unequal thickness, and they diminish somewhat in strength 

 anteriorly. 



