FAMILY VENERID^ VENUS. 219 



This beautiful little shell, which has been dredged from the East river near Blackwell's 

 island, was for a long time considered as the young of the common round clam. Col. Totten 

 first detected its specific identity. It occurs abundantly on all the sandy shores of Massachu- 

 setts, but its extreme northern and southern limits are not yet known. 



Venus pr^oparca. 

 (state collection.) 



Venus praparca. Say, Journ. Acail. Nat. Sciences, Vol. 2, p. 271. 

 V. notata, var.? Gould, Inveilebrala of Mass. p. 87. 



Description. Shell ovate, with numerous elevated subacute parallel concentric lines, which 

 subside into mere wrinkles near the suture of the ligament-slope ; interstitial spaces plain : 

 ligament-slope flattened, margined by an acute line. Anterior margin with an obsolete longi- 

 tudinal very obtuse undulation, which gives the tip of this margin a slightly truncated appear- 

 ance ; areola cordate, elevated at the suture : lower and posterior margins crenulated, the 

 crenulffi extending along the edge of the areola to the beak. In advance of the anterior ter- 

 mination of the ligament-groove of the left valve, is another distinct groove, which receives 

 the edge of the corresponding margin of the other valve. 



Color, white, immaculate; within, white or yellowish white. 



Vertical axis, 1*0 - 1'5 ; transverse ditto, 1"5 - 2 '2. 



This shell occurs frequently along our beaches, and is usually taken for the young of the 

 V. mercerania. Dr. Gould states that it seems to be same as V. notata, in which merely the 

 zigzag lines are wanting. It seems to me more widely transverse than either. 



{EXTRA-LIMITAL.) 



V. inequalis, Say. Shell subcordate, longitudinally sulcated : lines numerous, obsolete on the anterior 

 margin ; behind the middle, bifid, and alternating wiih smaller single ones : concentric distant 

 lamellar bands but little more elevated than the longitudinal lines. Anterior margin subangulated ; 

 within, the margin crenate ; crence obsolete on the anterior margin and rear. Hinge on the poste- 

 rior margin. Length, I'O; width, 1 '2. Coast of New-Jersey and Maryland. 



V. elevata. (Id. lb. p. 272.) Shell subcordate, longiuidinally sulcate : sulci equal, numerous, dense ; 

 on the anterior submargin sparse : concentric elevated remote lamellar bands. Anterior margin 

 subangulated at the tip ; within, margin crenate ; crenos obsolete on the anterior margin, and near 

 the hinge on the posterior margin. Length, 0*8; breadth, 0*9. Southern coast. 



V. mortoni. (Conrad, lb. Vol. 7, p. 251.) Shell very large, cordate, inflated, thick and ponderous, 

 with prominent recurved concentric laminse, more elevated on the anterior and posterior margins ; 

 ligament-margin arcuate. Umbones prominent ; lunule large, cordate, defined by a deep groove ; 



28* 



