Perkins.] 148 [November 3, 



sans Vert., Vol. vi, p. 846; Gould, Invert. Mass., p. 85, fig. 67; De 

 Kay, Moll. N. Y., p. 217, pi. xxvii, fig. 276. 



Common round clam. Occurs abundantly in sand just below tide 

 level. Animal with mantle open freely, except behind, where it is 

 united to form two very short siphons, which are blackish, fringed at 

 the ends, bright yellow inside; the mantle is thickened and ruffled 

 at the edge, yellowish white; gills, two pairs, greenish white, oblong- 

 ovate, somewhat pointed behind, hanging obliquely, inner a little 

 larger; foot rather large, when contracted broad and short, strongly 

 striated, somewhat crenulate on the lower edge, which is sharp, 

 broadest before and obtusely rounded behind, pointed bluntly, color 

 buff yellow; palpi lanceolate, smooth without, striated within; mus- 

 cles pink on the inner side, white on the outer, anterior pear-shaped, 

 posterior ovate. 



MEASUREMENTS. 



Length of shell 77 mill. Breadth 71 mill. Height 54 mill. 



" foot 37 " " 15 " anteriorly. 



" gills 28 and 29 " " 15 and 16.4 mill. 



" palpi 12.6 " " 7 mill. 



" siphon tube 14 " " 8 " 



As, according to the British Association rules, no specific name 

 can be made generic, those formerly given to this and the next 

 species do not hold. I therefore propose the names here given. 



Tottexia^x nov. gen. 



Tottenialilk gemma nobis. Gemma Totteni Stimps., Check 

 List, Venus gemma Totten, Am. Journ. Sc, Vol. xxvi, p. 366; 

 Gould, Invert. Mass., p. 88, fig. 51; De Kay, Moll. N. Y., p. 218, pi. 

 xxvii, fig. 271. 



Abundant in places, but not generally common. This species is 

 viviparous. In living specimens collected in the latter part of Jan- 

 uary, 1869, I found small, well formed young. There were in some 

 thirty six, but the average number was thirty three. These young 

 shells were oval, flat, transparent, longer than broad, the reverse of 

 what is usual in the adult, and in the same adult shell of nearly equal 

 size. In one shell, which contained thirty six, the young measured 

 three fifths mill, long and two fifths mill, broad, the adult shell being 

 three mill, long and three and two fifths mill, broad. I have changed 

 the name of this shell for the reason mentioned under the preceding 

 species. 



