165 



nearly spiral, and the other becoming larger, flatter, 

 and thinner; its substance is solid and brittle; the thin 

 part semitransparent, and slightly concave. 



All the examples the writer has seen of this shell, 

 were covered with a thin friable brown-colored epi- 

 dermis, over which the marginal edges of the posteri- 

 or parts are reflected; which occurrence is not noticed 

 by Lamarck. 



It is known to English collectors by the name of 

 Bulla dubia: and Sowerby mentions that there are 

 other species besides those enumerated by Lamarck. 

 Dolabella Rhumphii Dolabella fragilis. 



ONCHIDIUM. 



Cuviers Ann. du Mus. 5, p. 38, pi. 6. 



A mollusca without an interior shell, or external tes 

 taceous covering. Only two species are enumerated 

 by Lamarck but others are known to Cuvier. 

 Onchidium Typhae Onchidium Peronii. 



