venus. 327 



ment of the genus beyond the separation of Tapes and 

 Lucinopsis, I will indicate the divisions in the same way 

 as I have grouped other genera. Those belonging to 

 the genus Dosinia of Scopoli (Arthemis of Poli), Cy- 

 therea of Lamarck, and Timoclea of Leach are the 

 most remarkable; but the gradation from one to the 

 other, as well as from each to the typical form, is too 

 slight to warrant such a multiplication of names for 

 a few objects which, it must be confessed, are closely 

 related. In the species first alluded to, the siphon al 

 tubes are united for their entire length, which is not 

 the case in most other species. But nearly the same 

 diversity has been observed between individuals of the 

 same species (V. gaUina), and it exists also between 

 Tapes pullastra and T. decussatus, which clearly are 

 congeneric. The shell of V. exoleta (the type of Dosinia 

 or Artemis) differs little in shape from that of Circe or 

 of some varieties of V. fasciata. The type of Cytherea 

 (V. Chione) has an extra tooth and a nearly smooth 

 surface ; but in all other particulars it is a true Venus ; 

 and I agree with Mr. Clark that we have something 

 more to do than to " ring the changes on trivial points." 

 Callista was the name given by Poli to the animal of 

 Venus, Tapes, and Mactra. 



A. Mantle-tubes united throughout. Shell nearly orbicular, 

 concentrically imbricated; inside margin plain. 



1. Venus exole'ta*, Linne. 



V. exoleta, Linn. Syst. Nat. p. 1134. Artemis exoleta, F. & H. i. p. 428. 

 pi. xxiii. f. 3, 4. 



Body suborbicular, pale yellowish-white : mantle having its 

 edges fringed with close-set white cilia, which are most distinct 



* Worn awav. 



