198 Mr. G. B. Sowerby's observations 



XV.) that I have but slight reason for doubting their having been taken 

 from those two species. Deshayes's D. politicm is a very distinct species, 

 but as it also accords with Linne's description of D. politum, and as we 

 cannot now be certain to which Linne's description actually refers, it is 

 advisable to leave Deshayes's species in possession of this specific appel- 

 lation. 



21. D. translucidum. 

 I possess at least 1000 specimens of this species, of which a necklace 

 was composed which was brought from the Sandwich Islands. 



33. D. ehnrneum. 



The characters by which the species of Dentalia may be distinguished 

 are so few and difficult to seize, that among others it appears quite neces- 

 sary to recur to the characters which may be taken from the proportions. 

 It was this circumstance that induced me to give as a distinct species, the 

 one which I have called D. circinatum ; in mentioning this subject, al- 

 though Deshayes only gives this as a variety of Z>. eburneum, he furnishes 

 us with three characters by which it may be distinguished ; surely it 

 ought therefore to remain in the list as a distinct species, and the more 

 so, as these characters are not found only in one or two specimens, but 

 are invariable in a multitude of individuals. 



38. D. coarctatum. 

 The species described under this name is, I believe, distinct from that 

 published under the name of D. Gadus, by Montagu and Sowerby. It 

 cannot be the D. mimitum of Linne, not agreeing with his specific cha- 

 racter. 



Not being able to compare my specimens with those of Deshayes's 

 collection, I can only venture here to add two new species to the list, 

 which are as foUovi'S : 



D. opacum. 

 D. testa subrecta, attenuata, rapide majori, 17 vel 18 costata, fissura 

 postica brevi, dorsaU; long. 2^v^ diam. ^V? P"^'- 



