Portland and its Vicinity. 



327 



vicinity ; 



inform 



Island 



Sometimes these shells 



are scarcely changed in their appearance from recent 

 shells ; not even the epidermis being in all cases obliterated. 

 Bat generally, the cnvity originally occupied by the ani- 

 mal, is partly or wholly filled by an argillaceous hme- 

 stone. It is the same substance that is found very fre- 

 quently, in the same clay beds, in a concreted form ; and 

 in this state goes by the name of clay stones. In one or 

 two instances, where the cavity of the shell was only 

 partially occupied by this matter, I noticed minute crys- 

 tals of calcareous spar. Even where the whole interior 

 is filled with calcareous matter, the shell itself is not 



much altered. .. ■ ' 



The most common shell, and indeed the only one that 

 I found in much quantity, is a delicate species of Nucula. 

 I am assured by gentlemen well qualified to judge, that it 

 differs from all the recent species of that genus. I have 

 not had as much opportunity as I could desire, to ascer- 

 tain whether it is identical with any fossil species that 

 has been described. I presume it, however, to be unde- 



J- 



scribed, and venture to denominate it Nucula Port- 

 landicaJ^ 



* Dr. A. A. Gould has furnished the following specific description. 



Shell transversely ovate, convex ; posteriorly rounded, anteriorly- 

 acute and sub-plicate ; basal margin regularly rounded, obliquely 

 truncated anteriorly ; delicately striated transversely. 



Length seven twentieths, breadth twelve twentieths of an inch. 



Agrees with Lamarck's description of N. emarglnata^ as also with 

 the figure to which he refers, and which Brocchi gives as the Arca 

 pella^ L. except that it wants the oblique striffi. ^It differs, however, 

 from A. pella^ L. a recent species, as referred to by Lamarck in the 

 Encyc. Meth., in being less sloping and somewhat carinated ante- 



