1870.] 257 [Dall. 



Testa parva, tenui, compressa, ovali, pallide fulva minute transversim 

 striata, inazquilaterali, antice obiusa, postice longiore, subangulaia : striis 

 vix convexiusculis ; epidermide tenui, nitida, straminea induta ; umbon- 

 ibus parvis ; lunula cordata, polita; area nulla. Lon. 0.8; alt. 0.6; 

 lot. .2 poll. 



Distinguished by its oval shape, produced ventral margin, produced 

 and rounded extremities, compressed form and inconspicuous um- 

 bones. The. radiating striae are very faint and often wanting. The 

 concentric undulations are usually flattened, and the pallial sinus 

 rounded and very small. A beautiful variety from the Arctic Ocean 

 is of a delicate pea green, which pervades the soft parts as well as 

 the glossy epidermis. It is known from Nova Scotia, Hudson's Bay, 

 Ochotsk Sea, Kadiak, Fort Simpson in British Columbia, and the 

 Gulf of Penjinsk. The soft parts, especially the mantle and siphons, 

 differ from any described genus of Veneridse. There is no byssus 

 or byssal groove, nor any indication of a lateral tooth. The edge of 

 the mantle is smooth ; the soft parts are greenish white. 



I have seen a specimen from Penjinsk Gulf an inch and a half 

 long, and it grows to a considerable size on the Grand Banks. The 

 specimens obtained in Nova Scotia are usually rather immature, as 

 figured by Binney. 



Liocyma Beckii n. s. 



Testa ovato-trigona, subasquilaterali, tumida, nitidissima ; irregu- 

 lariter concentrice. sulcata; alba dut lutescente; margine dorsali vix 

 angulato; lunula lanceolata, nitida, linea parum inconspicua circum- . 

 scripta : ligamento inconspicuo, insesso ; area nulla; sinu palliari 

 parr o, angulato ; margine integro ; umbonibus prominent ibus ; dentibus 

 cardinalibus in utraque valva tribus divergentibus, dentibus lateralibus 

 nullis. Lat. 0.4; Ion. 0.56; alt. 0.54 poll. 



Distinguished by its rounded umbones and moderate tumidity, by 

 the angulated hinge margin, short, anterior extremity, less arcuated 

 ventral margin and small size. The, area occupied by the hinge 

 teeth, is shorter and wider than in the last species, from which its tri- 

 gonal shape immediately distinguishes it. Over one hundred speci- 

 mens were collected at Plover Bay, E. Siberia, agreeing with each 

 other and differing from the young of the last species, as above. 

 One specimen was dredged alive at Ounga Island, near Aliaska. The 

 soft parts were white, and the siphons of a deep pink, darker toward 

 the ends. The pallial line is very broad. 



PROCEEDINGS B. S. N. H— VOL. XIII. 17 ArR.IL, 1870. 



