JUKES-BKOWNE : CRETACEOUS AND EOCENE VENEEID^. 155 



p. 113), but they really belong to the section Macrocallista of Meek 

 (op. cit., 1876, p. 177). C. Icevigata (Lesh.) (PL VI, Fig. 5), at any 

 rate, is referable to this section, while C. proxima and C. suherycinoides 

 are similar in shape and in hinge-characters ; but I have not seen 

 specimens of C. Heherti (J)es\i.), the hinge of which, as figured by 

 Deshayes, seems to resemble that of Pitaria. 



Three other Eocene species of CkiUista were separated by 

 M. Cossmann under the name of Chionella, and though he recognized 

 their resemblance to Cytherea chione in shape and in surface- characters, 

 he appears to have regarded them as more closely related to Pitaria 

 than to other sections of the old genus Cytherea. In this view I find 

 myself unable to concur, for I cannot see that they diff'er in any 

 essential particular from recent forms of the C. chione group. 

 Dr. W. H. Dall came to the same conclusion in 1902,^ and as he did 

 not recognize the name Callista he adopted Chionella as applicable to 

 the whole of the large group of recent shells, which includes C. chione, 

 though he was obliged to make it a section of a genus Macrocallista 

 (Meek). I see no reason for this method of procedure, but regard 

 the name Chionella as merely a synonym of the Callista of Morch and 

 of Meek. 



I am indebted to M. Cossmann for sending me specimens of his type 

 species of Chionella {Ch. ovalina, Desh.), and these I have carefully 

 compared with young specimens of Callista chione and other species 

 of the genus. The hinge of C. ovalina is identical with that of 

 Callista, and the only point in which the shell differs from the 

 generic type is the rounded and slightly ascending pallial sinus, 

 a character which is common to many of the Eocene Venerida^, and is 

 not sufficient to warrant even sectional separation. 



There remain, however, some other contemporaneous species which 

 have the hinge of Callista, but differ in the surface sculpture of the 

 shell, this consisting either of fine concentric striae like those of Pitaria 

 or else of sharp concentric ribs like those of Hysteroconcha ( Venus dione, 

 Linn.), and in neither case showing any trace of the minute radial 

 markings of Callista. By M. Cossmann these species were distributed 

 under several of his sections, without sufficient regard to the details 

 of the hinge. I propose to separate them under the name of 

 Calpitaria, to indicate its connection with both Callista and Pitaria, 

 and would define the group as follows, taking C. sulcataria, Desh., as 

 the type. 



Calpitaeia, n.subgen. 



Shell ovate, fairly convex, concentrically striated or sharply ribbed. 

 Cardinal teeth like those of Callista, anterior and median cardinals of 

 left valve united at the top and barely reaching to the shell-border, 

 anterior pit in right valve deep, and generally separate, but sometimes 

 having a narrow thread-like channel which passes in front of the 

 anterior cardinal. Pallial sinus generally short, and always rounded, 

 varying in direction from horizontal to ascending. 



Synopsis in op. cit., p. 351 ; see also Waguei', Free Inst, of Science, vol. 

 p. 1252 (rhiladelphia, 1903). 



