TO GEOLOGY. 95 



Two species only of this genus seem to have been ob- 

 served in England, neither of which belongs to the London 

 Clay. The clathrata has been found in the Great Oolite 

 the graca in the Crag. In the Tertiary Tables of M. Des- 

 hayes we have eight species, four of which are from the 

 Paris basin. From the Maryland deposit we have two 

 species, .F. redimicula (Say), and F. grceca (Lamarck), 

 specimens of both of which may be seen in the Academy 

 of Natural Sciences. Of the grwca being the anologue of 

 the West India species I have great doubt. 



GENUS HIPPONIX. Defrance and Blainmlle. 



H. pygmwa. Plate 3. Fig. 75. 



Description. Shell subrotund, obliquely conical, closely 

 ribbed ; apex straight, pointed ; cicatrices impressed ; mar- 

 gin entire. 



Long. diam. .2, Transv. diam. 3-20ths, Height nearly .1 ,of an inch. 



Figure magnified. 



Observations. This interesting little shell has a strong 

 resemblance in form to H. cornucopia (Defrance and Blain- 

 ville), Pileopsis cornucopia (Lamarck). I have determined 

 to place it in that genus in consequence of its possessing 

 the horse shoe shaped cicatrix mentioned by Blainville,* 

 although I have not seen it attached to any support. 



* Manuel de Malacologie, &c. p. 507. 



