1 1.2 Mr. W. King on a British Shell of the genus Circe. 



XV. — Note on a British Shell of the genus Circe. By William 

 King, Curator of the Museum of the Natural History Society 

 of Northumberland, Durham, and Newcastle-upon-Tyne. 



The Linnsean genus Venus has of late been very much subdi- 

 vided by some conchologists, so that in addition to Lamarck^s 

 Cytherea and Polios Artemis, we have now the genera Circe, Chione, 

 Meroe, and several others. 



Chione, as its name implies, is represented by such shells as Cy- 

 therea Chione and C. Erycina. Circe, according to some shell-labels 

 in the British Museum, is represented by Cytherea scripta and 

 C. divaricata. Circe somewhat resembles Chione in its teeth, but 

 it differs from the latter in the pallial impression being slightly 

 inflected, and in the cartilage fulcra being deeply sunk. 



There appear to be three or more sections of the genus Circe. 

 In one the species have transverse ribs (C (Cytherea) arabica) ; 

 in another they are furnished with diverging longitudinal ribs 

 (C. [Cytherea) divaricata) ; and in the third they are very. much 

 compressed, especially at the umbones (C. [Cytherea) scripta). 



I have entered upon this note with the view of showing that a 

 British shell which has hitherto been called Cyprina triangularis^ 

 belongs to the genus Circe. I was first led into this opinion from 

 examining some specimens belonging to Mr. J. Alder, who 

 dredged them in Oban Bay during the last summer. 



The so-called Cyprina triangularis is decidedly a Circe, inas- 

 much as it possesses what appear to be the distinguishing cha- 

 racters of the genus, namely deeply-sunk cartilage fulcra, and a 

 slight sinus in the pallial line. I may even go so far as to say, 

 that it belongs to the section represented by the transversely 

 ribbed species. As regards the dental character of the Oban 

 shell, it is precisely that of the genus in general, — consisting of 

 three diverging cardinal teeth in each valve, and an anterior tooth 

 in the left one. It also possesses a well-defined lunette as in the 

 Venuses, with which it further agrees in the absence of an epi- 

 dermis. 



In the deeply sunk cartilage fulcra, and the dental character 

 just given, — in the possession of a well-defined lunette t, and in 

 the want of an epidermis, the Oban shell is essentially different 

 from all the true Cyprinas, either recent or fossil % . Leaving out 



* Turton's Shells of the British Islands, p. 133. tab. 1 1. figs. 19 and 20. 



■\ According to a figure in D'Orbigny's ' Terrains Cretaces,' pi. 271, a 

 species of Cyprina has a well-defined lunette. 



X The genus Cyprina may be safely considered as represented by C. 

 islandica (recent), C. rnstica (Suffolk crag), and C. angulata (greensand). 

 Many of the so-called Cyprinas do not appear to belong to this genus : Cy- 

 prina consobrina (D'Orbig.), notwithstanding its want of a pallial sinus, I 

 consider a Venus ; and Cyprina Mmrisii (J. de C. Sow.) has teeth after the 

 type of Cytherea Lamarckii. 



