JUKES-BROWNE : ON CALLISTA, AMIANTI8, AND PITARIA. 341 



interpreted their dentition in the same manner as Dr. Dall and 

 myself;' but as tlie true construction of tlie Callocardia hinge 

 was unknown to him, he retained the latter in the Cyprinida) and 

 placed Atopodonta with a (?) in the Veneridae. As I have pointed 

 out, the arrangement and form of the teeth in Atopodonta are not 

 quite the same as in Callocardia; the former must therefore be 

 regarded as a section of the latter, though no doubt it is really the 

 ancestor of Cdllocardia, and is at j)resent only known to occur in 

 the Eocene of the Paris Basin. 



There only remains the genus Vesicomya to be considered, and by 

 the kindness of Mr. MacAndrew I have been able to examine a good 

 specimen of V. lepta. This has convinced me that Vesicomya cannot 

 be placed in the same genus as Callocardia, nor even in the same 

 sub-family, for it does not possess any lateral teeth. Tlie hinge-plate 

 is long and narrow, extending beyond the teeth at each end, and 

 turned up slightly on the anterior side of both valves, but this is 

 clearly due to the attachment of the pedal muscle. There are only 

 three teeth in each valve, and these are laterally elongated, pulled 

 out as it were, the united median and anterior of the left valve being 

 both directed forward, while the right anterior is high up near the 

 lunular margin, and the median is placed below it and projects 

 a little beyond it. The right posterior is a double tooth consisting 

 of two separate laminae, of which one is united to the anterior tooth. 

 This arrangement of teeth differs from that of any other genus, but 

 comes nearest to wliat is found in the fossils Cyprimeria and 

 Cyclorisma. There is an additional point of similarity in tlie fact 

 that some species of Vesicomya (like V. lepta) have no pallial sinus, 

 wliile others (like Leeana, Dall) have a fairly deep one, and for the 

 latter Dall proposed the name Callogonia. 



Having satisfied myself of the existence and convenience of these 

 generic groups so far as recent shells are concerned, I thought it 

 desirable to re-examine some of the Eocene fossils which were dealt 

 with in a former paper,^ in order to see how they could be classified 

 by the hinge cliaracters above indicated. 



It will be remembered that a certain number of these Eocene 

 fossils seemed to combine some of the characters of Pitaria with some 

 of Callista, and that for these I proposed to create a section under tlie 

 name of Calpitaria, with P. salcataria, Desh., as the type. I now find 

 that this estimate of their taxonoraic position is curiously confirmed 

 by the form of the left posterior cardinal, which in these species is 

 closely appressed to the nymph for part of its length, hut is 

 slightly curved at the end so as to disengage itself and extend 

 across the hinge-plate. It thus occupies a position which is 

 intermediate between that of the same tooth in Callista and that 

 in Pitarina. 



From specimens which I owe to the kindness of M. Cossmann, 

 I find that this is the case with P. sulcataria and its var. Suettonensis, 



1 Manuel de Conchyliologie, 1887, p. 1088. 

 - Proc. Malac. Sec, vol. viii, p. 148, 1908. 



