161 



Cyclas c(erulea. C. testa tenui, fragili, subovata, subequi- 

 laterali, postice abrupta, umbonibus tumidis, non' approximatis. 

 Long. 0.31 ; lat. 0.29 ; diam. 0.19 inches. Hob. Massachu- 

 setts. 



Shell delicate, posteriorly abrupt, beaks tumid. Color grayish 

 blue, striations not visible. 



Remarks. At first sight this species might be taken for the 

 C. partumeia of Say, but it is much less convex, posteriorly less 

 angular, and the beaks are less tumid ; compared to the C. cdly- 

 culata of Draparnaud, found by Professor C. B. Adams, in Ver- 

 mont, it is generally less angular, the beaks are less approximate, 

 and it is also rather more convex. The animal is also different 

 from that of the C. partumeia of Say, being of a much lighter 

 red color. 



I discovered this species this autumn very plentifully in a clay 

 pit near Fresh Pond, Cambridge. Cabinet of the Boston Society 

 of Natural History. 



Cyclas tenuis. C. testa minuta, alba, nitida, tenui, subo- 

 vata, elongata, postice subtruncata, umbonibus prominentibus, 

 apiculatis, tuberculosis. Long. 0.26 ; lat. 0.19 ; diam. 0.15 

 inches. Hah. Massachusetts. 



Shell small, fragile, elongated, rather ovate, posterior some- 

 what abrupt, anterior and inferior margins rounded, beaks situ- 

 ated towards the anterior, bearing a resemblance to prominent 

 tubercles, hinge margin nearly on a straight line, teeth minute, 

 surface smooth, strise very fine ; color light brown, with a broad 

 zone of yellow on the margins. 



Remarks. This beautiful little species I discovered last spring 

 in a small stream in the vicinity of New Bedford. In outline it 

 somewhat resembles the C. transversa Say, but independent of 

 the difference of size, it is less inflated, and the beaks are not as 

 large, or as rounded. 



2. GENUS PISIDIUM. 



PisiDiuM OBSCTjRUM. P. tcsta magna, subglobosa, tumida, 

 tenui, fragili, tenuiter striata, postice brevi, umbonibus magnis, 

 elevatis. Long. 0.26 ; lat. 0.20 ; diam. 0.15 inches. Hah. 

 Ohio. (Adams.) 



PRonEErtlNGS B. S. N. TT, 11 MARCH, 1850 



