378 PROCEEDINGS OF THE NATIONAL MUSEUM. 



VENUS CAMPECHIENSIS var. TEXANA Dall, 1902. 



Texas coast. 



Shell suborbicular, inflated, with the concentric lamellaj toward the 

 middle of the disk coalescent, forming broad, more or less inosculating, 

 low, flat-topped ribs w' ith polished tops, sometimes showing the brown 

 lineations of the younger stages. 



VENUS CAMPECHIENSIS var. TETRICA Conrad, 1838. 



Shell with the size and dense surface sculpture of the typical form 

 but the produced trigonal outline of V. ineTcenar'ia. 



VENUS CAMPECHIENSIS var. CUNEATA Conrad. 1868. 



Shell subtrigonal, yery thick, with yery prominent beaks, and very 

 short and blunt, the antithesis of the elongated variety tetrica. 



VENUS CAMPECHIENSIS var. CAROLINENSIS Conrad, 1875. 



Shell much like the normal form but with the lamellae more or less 

 coalescent in the middle of the disk and not flattened or polished. 

 This occurs living and also in the miocene of North Carolina, from 

 which it was described. 



LIOCYMA FLUCTUOSA Gould, 1841. 



Arctic, Spitsbergen, and Greenland seas, and the Sea of Okhotsk; 

 southward to the Gulf of St. Lawrence and Nova Scotia, on the 

 Atlantic coast. 



The typical form is cream}^ white. A variety hrunnea^ of rich 

 chestnut or yellow l)rown, is noted from the Gulf of St. Lawrence. 

 It is the Venus astartoides (Beck MS.) Philippi, 1849, but not of 

 D'Archiac, 1847. Tapes arctica Reeve, 1864, from the ""Arctic Seas," 

 though not this species, may belong to this group. 



GEMMA GEMMA Totten, 1834. 



Labrador to Woods Hole, Massachusetts; New York Bay? 



Flatfish and irregularly rippled concentrically. The type is more 

 or less purple, var3dng to pure white, which forms the variety Manhat- 

 taiumsis Prime, 1862. The species is Gemma totteni Stimpson, 1860, 

 and Tottenia gemma, Perkins, 1869. 



GEMMA (GEMMA var.?) PURPUREA H. C. Lea, 1842. 



Cape Cod to the Bahamas and Texas. 



More inflated, trigonal, and with uniform concentric threads sharply 

 defined. It is Gemma concentrica Dall, 1889. The color is variable, 

 but usually paler than G. totteni. 



1 



