81 



NOTE ON THE GENERA CALLOCARDIA AND YESICOMYA. 



By Edgar A. Smith, F.Z.S., etc. 



Read 9th March, 1900. 



The genus Callocardia was founded by A. Adams 1 upon a single left 

 valve, dredged off the Island of Qnelpaart in 48 fathoms. His 

 description of the hinge-teeth would not lead one to suppose that the 

 shell in question really belonged to the Veneridae, and was inseparable 

 from Caryatis, a subgenus of Meretrix, as already pointed out by 

 Sowerby, 2 who did not, however, describe the hinge in detail, but 

 merely observed that it was almost identical with that of Caryatis 

 Sung erf ordi, which he described at the same time. 



Having recently examined examples of Callocardia Stearnsii, Dall, 

 and C. lepta, Dall, I was glad of the opportunity of comparing them 

 with the type of the genus, and at the same time with C. Atlantica, 

 Smith, C. Pacijica, Smith, and C. Adamsii, Smith, which I had 

 doubtfully assigned to Callocardia in the report on the " Challenger" 

 Pelecypoda. The result of this examination would seem to show that 





Fig. I. — Caryatis isocardia. 



Mr. Sowerby was quite right in uniting Callocardia with Caryatis, 

 and that the other above-named species do not belong to that genus, 

 but should be placed in Vesicomya, which was described by Dall 3 as 

 a subgenus of Callocardia, for the reception of the three above-named 

 "Challenger" species with C. pilula, Dall, C. venusta, Dall, and 

 C. subquadrata (Jeffr.), Dall, since named C. (Ves.) Dalli by Verrill 

 and Bush. 



One of the perfect examples of Callocardia guttata, A. Ad., the type 

 of the genus (= Cytherea (Caryatis) isocardia, Sby.), mentioned by 

 Sowerby, was obtained for the Museum, thus enabling me to compare 

 both valves with typical species of Caryatis. The hinge of the left 

 valve is described by Adams as consisting of two teeth with a narrow 

 curved pit between them. The anterior tooth is said to be very 

 prominent, angularly bent in the middle, with an anterior and 



1 Ann. & Mag. Nat. Hist., vol. xiii (1864), p. 307. 



2 Proc. Zool. Soc, 1888, p. 218. 



3 Bull. Mus. Comp. Zool., vol. xii, p. 272. 



