88 1NVERTEBRATA OF MASSACHUSETTS. 



valve, the middle one cleft in both valves ; muscular and palleal 

 impressions very superficial, the latter with a deep sinus. Length 

 | inch, height | inch, breadth 3% inch. 



Of this shell I have three specimens brought from the Bank fish- 

 eries. The largest specimen is proportionally more convex than the 

 others, and the ridges are less definite. The ridges and grooves of 

 the surface are like those of V. papiliondcea. 



I know of no species very closely approaching this. Most of those 

 allied to it have the posterior extremity more or less angular ; this is 

 always accurately rounded. Venus cenea of Turton, small specimens 

 of V. gallina, and of those Indian species allied to V. papiliondcea^ 

 may be mentioned as allied to it. 



VENUS GEMMA. 



Shell minute, nearly round and nearly equilateral, concentri- 

 cally furrowed, violet and white, margin crenulate. 



FIGURE 51. 

 State Coll., No. 194. Soc. Cab. No. 2334. 



Venus gemma, TOTTEN ; Silliman's Journ., xxvi. 367. f. 2, a, b, c, d. 



Shell small, nearly orbicular, beaks nearly central, slightly ele- 

 vated ; generally eroded. No defined lunule in front of them ; 

 surface shining, with minute, concentric, crowded furrows ; ante- 

 rior portion, and mostly the base, white or tinged with rose- 

 color ; posterior and upper portion reddish-purple ; within white, 

 except posteriorly, where it has the purple color of the outside ; 

 muscular and palleal impressions distinctly marked, the latter with 

 an acute sinus ; teeth divergent, the middle one in each valve 

 stout and triangular, the anterior tooth of the right, and the poste- 

 rior one of the left valve thin, and not easily distinguished ; inner 

 margin crenulated. Length ^ inch, height ]- inch, breadth ^ inch. 



This beautiful little amethystine gem, as it has been appropri- 

 ately called, is found in great abundance on all the sandy shores of 

 Massachusetts Bay. Col. Totten also found it in Newport har- 

 bour. Beyond this, its range is not known. It was noticed by 

 some of the early visiters to New England, and specimens of it 

 were sent home to England among other curiosities. It is, 



