Post-tertiary Fossils and Recent MoUusca. 239 



NaturaB ' three names given for the same species, viz. Mya 

 arctica^ Solen minutus^ and Mytilus rugosus. None of them 

 appeared in any of the prior editions. The only reference 

 made to other works is in the case of Mytilus rugosus^ where 

 Lister's ' Animalia Angliae ' is quoted ; and there can be no 

 doubt that the quotation is correct. Hanley regarded Mytilus 

 rugosus and Mya arctica as distinct species ; and in his 

 ' Ipsa Linn^ei Conchylia ' he says, as to Mytilus rugosus^ that 

 the only shells in the Linnean collection " contained in the 

 box thus marked in the cabinet are worn full-aged specimens 

 of Saxicava arctica or Hiatella ohlonga of Turton." This 

 species has no end of other synonyms. 



Trichotropis tenuis^ Smith. 



In Littorina litorea and Fusus antiquus the same kind of 

 distortion is observable. The mouth of the shell becomes 

 more rounded or circular, and the base is more or less umbi- 

 licated. The earlier growth of the shell is quite regular in 

 distorted specimens of the common periwinkle and almond- 

 whelk ; and usually the last whorl only in such sj^ecimens is 

 abnormal, probably in consequence of the mantle being then 

 injured. 1 must venture to regard the present so-called species 

 as a monstrosity of T. hicarinata. 



Bucciymm sericatum, Hancock. 



Mr. Smith's description and figure of the radula do not 

 quite agree with the description given by Mr. Jabez Hogg in 

 my preliminary report of the ' Valorous ' cruise (Proc. Roy. 

 Soc. no. 173, p. 201), nor with his drawing, which were 

 taken from a full-grown specimen of what I consider the 

 same variety of B. Groenlandicum. The only difference con- 

 sists in one of the lateral plates shown in Mr. Smith's figure 

 having two fangs instead of three ; and it may be ac- 

 counted for by Mr. Smith's specimen being young. I sus- 

 pect that the figures in Troschel's ' Gebiss der Schnecken,' 

 Bd. ii. L. ii. T. vi. f. 12 and 13, have been accidentally 

 reversed, and that f. 12 belongs to B. glaciale and 13 to B. 

 Groinlandicum. As to the epidermis, I concur with Dr. Morch 

 in the remarks which he published in the last number of the 

 ' Journal de Conchyliologie,' p. 267, viz. : — ' L'epiderme des 

 i5uccins et dcs Fuseaux est extremcment variable et n'ofFre 

 qu'tl peine des caracteres spccifiqucs constants. Ainsi, le 

 Buccin onde possede, tant6t un epiderme lisse et mince, tan- 

 tot un epiderme cilie et (';pais. La premiere forme se trouve 

 chez les individus qui vivent sur un fond rocailleux ; la der- 



