MUSEUM OF COMPARATIVE ZOOLOGY. 297 



present one. Had Miss Bush in her excellent paper had more material, she 

 would probably have hesitated to give a name to the pretty species she has 

 called costata. Her distinctions from ornatissima are that the ribs are less 

 numerous, more curved, and the shell less convex in the Carolina specimens. 

 I find in her figure eight visible ribs; in seven valves from the Carolina coast 

 I find the ribs varying from five to seventeen; the strong ones extending to the 

 beaks number from five to eight; their curvature varies somewhat. The di- 

 ameter of D'Orbigny's figure relative to its height is as 11 : 14, while in Miss 

 Bush's specimens it is, she states, as 4 : 4, so that her specimens were really 

 more convex than D'Orbigny's, rather than less so. But his figures, made in 

 1840 or so, and much magnified, must not be construed too literally, as they 

 are on the face of them a little formal, though excellent for the time. 



Cardiomya costellata Deshates. 



Corhula costellata Desh. Expl. Sci. Morea, Geol., p. 86, pi. vii. figs. 1-3, 1837. 

 Necera costellata Jeffreys, Brit. Coneb., III. p. 49 ; V. p. 191, pi. xlix. fig. 3 ; P. Z. S , 



1881, p. 944. 

 Neoera curta Jeffreys (name, no description), Valorous Moll., Ann. Nat. Hist., 1876, 



p. 495 ; P. Z. S., 1881, p. 943, pi. Ixxi. fig. 10. 

 Sphena alternata D'Orbigny, Moll. Cuba, II. p. 286, 1846 ; Atlas, pi. xxvii. figs. 



17-20, 1845. 

 ? Necera alternata (D'Orbigny) Dall, Bull. M. C. Z., IX. p. 110, 1881. 



A fine series of specimens in the Jeffreys collection, especially from the 

 Mediterranean, is sufficient to convince the most sceptical of the great vari- 

 ability of this species. It varies from smooth, or with but two or three radi- 

 ating costse, to completely radiated all over; the rostrum varies in actual and 

 in relative length and direction; the amount of inflation, its direction, and 

 consequently the outline of the shell, vary considerably. The European speci- 

 mens sometimes have a smooth interval between the end of the rostrum and 

 the radiating sculpture of the body, and sometimes the whole is covered' with 

 radii. The most common form seems to be that in which there are compara- 

 tively few and rather strong radii on the posterior part of the shell, with the 

 rest smooth or faintly radiated, and the rostrum smooth, except a few radii on 

 its dorsal side, and rather long. This form has been collected by Hemphill in 

 two fathoms at Marco, Florida, and has been dredged by the U. S. Fish Com- 

 mission at Stations 2597, 2602, and 2614, off the Carolina coast. These are all 

 small, Jeffreys' finest British specimens being about 10 mm. long, and the 

 average length of those from all localities being about 6-7 mm. The form 

 named curta by JeS"reys (which may rank as a variety though connected by 

 indefinite gradations with the type) is also small, and has the rostrum short 

 and recurved, the striation strongest posteriorly but varying, as in the type. 

 Some of the specimens dredged by the U. S. Fish Commission at Station 2602 

 were of this variety. 



