RHYXCHONELLA. 209 



by Liiinoeus, Mliller, and Chemnitz, and a comparison of them 

 with oar shell had well satisfied me of their correspondence. The 

 downy epidermis is a character too rare and singular to be over- 

 looked. This, however, is ruljbed off very easily. The shell is 

 much thinner, in general more elongated, and the strias nearly 

 twice as numerous, being about thirty to forty in the European, and 

 fifty to sixty in the American specimens. No account of the in- 

 ternal bony processes is given in any description except that by 

 Mr. Couthouy. These would afford the best possible specific char- 

 acter, were it not that they are usually more or less broken. But 

 I have been relieved from all further speculation by the receipt of 

 specimens from Dr. Loven, which settle the identity of our species 

 with the European capiil-serpentis. Deshayes conjectures, proltaldy 

 with justice, that the Anomia aurita of Gmelin is the same thing ; 

 and also, that Anomia pubesccns of the same author and others is 

 this shell in a young stage, when plentifully coated with pubescence. 

 T. custala, descriljed and figured by Lowe, in the " Zoological 

 Journal," ii. 105, pi. 5, figs. 8, 9, is very closely allied ; but it is a 

 smaller, more solid shell, with fewer riljs, and entirely different 

 internal processes. 



[I have retained the al)Ove remarks from the former edition, l)e- 

 cause our shell is so generally still regarded as identical with the 

 Eurojjean species. But further examination of numerous specimens 

 has led me to coincide with Dr. Stimpson, who has dredged exten- 

 sively, l)oth in the British and American seas, in his opinion that 

 " the species differs from the European cuput-serpenlis sufficiently in 

 both shell and animal." 



Family RHYNCHONELLID^E, D'Okbigj^y. 



Shell with radiating ribs, the arm supports long, slender, simple, 

 and gently curving towards each other ; no area ; the opening for 

 the pedicle usually completed by two small pieces ; animal with 

 elongated spiral arms. 



Genus RIIYl\CHO]^EL,L,A, Fischer. LS09. 



Shell triangular, acutely beaked ; usually plaited ; large valve 



elevated in front, depressed at the sides ; small valve flattened or 



hollowed along the centre hinge-plate with two slender curved 



processes. 



14 



