340 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



declared that so far as the hinge is concerned there is no essential 

 difference between Callocardia and Caryatis. He also figured the 

 hinge of Vesicomya lepta for comparison, but did not discuss the 

 generic affinities of tlie latter, thus leaving us under the impression 

 that it was akin to Ccillocardia. It is noticeable, however, that lie 

 writes of Vesicotnya as a genus, and that his list of species which 

 probably belong to it comprises all the forms which had been 

 described by Dr. Dall and himself under the names of Callocardia, 

 Vesicomya, and Calloyonia. 



The figure of the Callocardia hinge is not very good, and does not 

 clearly bring out the existence of the anterior lateral in the left 

 valve, but Mr. Smith informs me that it is there — " an erect acute 

 tooth arising from the margin of the hinge-plate." He further tells 

 me that he does regard C. guttata as merely a species of Pitaria, the 

 fact of the united cardinals in the right valve not reaching the dorsal 

 margin in some species being in his opinion of no great importance. 

 On this point I agree with Mr. Smith, and differ from Dr. Dall, 

 who makes Callocardia a genus with a sub-genus Agriopoma on the 

 strength of it. I think, however, that the hinge of Callocardia has 

 some features which are more than specific, and if it really has an 

 entire pallial line it maj' remain as a sub-genus of Pitaria. 



The only other shell which can be placed with Callocardia gtdtata 

 is that described by Dr. Dall in 1889 as Veneriglossa vesica, but 

 afterwards regarded by him as a species of Callocardia.^ It was 

 described as having a hinge like Cytherea, but with an entire 

 pallial line. 



The shell described by ^Iv. H. B. Preston in 1905 under the name 

 of Callista {Callocardia) Birtsi only resembles Callocardia in being 

 a thin white shell with some resemblance to Pitaria. Its dentition 

 is like that of Lamelliconcha and Pitaria tumens; the hinge-plate is 

 deeply excavated and attenuated posteriorly, but all the teeth are 

 very short, tall, and narrow, except the left posterior cardinal, which 

 is a short low inconspicuous lamina under the umbo, and confluent 

 with the nymph. The pallial sinus is obscure, but is rather short 

 and rounded. The lunule is superficial, not impressed, and there is 

 no escutcheon. 



There are several shells which are similar to C. Birtsi, namely 

 Caryatis JJesIiayesi, Fh\, C. Hungerfordi. Sow., C. pudicissima, Smith, 

 a fine shell which may be a variety of Peshayesi in Mr. MacAndrew's 

 collection, and another unnamed species from the Persian Gulf in 

 ]Mr. J. C. Melvill's collection. All these are thin, white, oval sliells, 

 concentrically striated, and slightly angulated on the posterior slope. 

 For this small group I propose the name of Leucothea with L. Birtsi 

 as the type, and would place it as a sub-genus of Pitaria, as a link 

 between the typical section and Callocardia. 



The fossil "shells described by M. Cossmann in 1886 under the 

 generic name of Atopodonta are closely allied to Callocardia. When 

 referring to them in 1908 I omitted to notice that P. Fischer had 



1 See Bull. U.S. Nat. Mus., vol. xxvi, p. 353, 1902. 



