DALL : ON THE GENUS GEMMA, DESHAYES. 239 



Gould says^ under Venus, which is defined as having three cardinal 

 teeth in each valve, Venus gemma (fig. 51) has "no defined lunula," 

 "teeth divergent, the middle one in each valve stout and triangular, 

 the anterior tooth of the right, and the posterior one of the left valve 

 thin and not easily distinguished." He does not mention the lateral 

 teeth, though he indicates the grooving ol the anterior lateral margin 

 in his figure of the left valve, which is not particularly characteristic, 

 being mostly copied from that of Totten. In 1842 Dr. Gould" refers 

 the then recently described Cyrena ptirpurea H. C. Lea, from Delaware 

 Bay, to a small specimen of Venus gemma Totten. 



Gould's (1841) description is copied and the shell very badly figured 

 by DeKay.-' In the same year Dr. Mighels^ referred to it as an 

 abundant littoral shell on sandy or muddy shores all along the coast 

 of Maine. 



In the supplement to Jay's "Catalogue of Shells in his collection," 

 printed in 1852 (Ed. 4, suppl. p. 466), the name " Venus manhattan- 

 ensis, Prime, Mss.," appears but without any description or figure. 



In 1853, Deshayes^ creates the genus Gemma, not knowing the 

 soft parts ; he places it next Mercenaria, in the section Venusina, 

 or typical Venerids, without lateral teeth. He allows the new genus 

 two cardinal teeth in the right valve and three in the left valve, and 

 says nothing of the lunule. 



In 1883, Sowerby figures the Massachusetts Bay form.*' A few years 

 later H. & A. Adams, quoting their text and locating Gemma after 

 Deshayes, figure the shell of a Massachusetts Bay specimen. The 

 drawing has been modified on the plate after it was first engraved, but 

 does not clearly exhibit the true characters of the hinge, and probably 

 was made from an imperfect specimen. They adopt the name of 

 Gemma gemma, as used by Deshayes. 



Following the example of many of the older naturalists when a 

 specific name had been taken for generic use, Stimpson" proposed a 

 new specific name Tottenii for the Ve^ius gemtna of Totten and the 

 Gemma gemma of Deshayes. 



In 1862, Prime*^ described and figured the Venus manhatlanensis 

 mentioned ten years before in Jay's "Catalogue," under the name of 

 Venus (Gemma) 7nanhattane7isis, According to Prime, his species 

 differed from the type of the genus in being "smaller, more triangular, 



1 " Invertebrata of Massachusetts," 1841, p. 88. 



2 Proc. Boston Soc. Nat. Hist., vol i, p. 61. 



3 " New York Mollusca," p. 218, pi. 27, fig. 177, 1843. 



4 Boston Journ. Nat, Hist., vol. 4, p. 321. 



5 "Cat. Conch. Brit. Mus.," part i, pp. 112-113. 



6 Thesaurus, Monograph of l'e}it(s, vol. 2, pi. 158, fig 141, p. 737. 



7 "Check List of Shells of the East Coast of North America," published by the Smithsonian 

 Institution in June, i860, p. 3, no. 174. 



8 Ann. Lycetiiit Nat, Hist. N.'\'., vol. 7, p. 482, 



