118 CONTRIBUTIONS 



furrow, smaller striae may be perceived. In the umbilicus 

 the striae on the inferior part of the whorl are longitudinal 

 on the superior part transverse. The two carinae cause 

 the lip to be slightly angular. 



D. depressa. Plate 4. Fig. 105. 



Description. Shell sublenticular, polished, obsoletely 

 and transversely striate, substance of the shell thick ; spire 

 depressed ; suture slightly impressed ; umbilicus rather 

 small, thickened and wrinkled at the edge ; whorls three ; 

 mouth subelliptical. 



Length nearly .1, Breadth .2, of an inch. 



Observations. Of this curious and interesting little 

 species, I have procured but a single specimen. Its 

 smoothness and general form are very unusual in this 

 genus. Its lenticular form causes the mouth to be some 

 what oval. A small portion only of the lip is perfect, and 

 it seems to be thickened and somewhat reflected. 



De la Beche mentions an undetermined species as ex 

 isting in Yorkshire, as low down as the Oolitic Group. 

 Sowerby does not describe any, in his &quot; Mineral Con- 

 chology.&quot; M. Deshayes, in his excellent Tables, gives 

 twelve for the Tertiary. There are eight in the Paris 

 basin, and five in the London basin. 



I believe none have been heretofore observed in our de 

 posits. 



