THE NAUTILUS. 47 



Mya riigidosa, Wood. 



Alasmodon marginata, DeKay, Gould. 



Margaritana marginata, Lea. 



Shell ovate, thin, wedge-shaped, gaping widely behind ; beaks 

 small, elevated ; surface wrinkled posteriorly ; epidermis olivaceous^ 

 radiated with dark green ; teeth, one in each valve, small, compressed, 

 directed forwards; nacre bluish-white with a chalky margin. 

 Length, 2 inches; height, ItV inch ; breadth, /o inch. 



This species is not all common in New England, and is found very 

 sparingly in the Blackstone River, just above the Tin Bridge in 

 Central Falls. 



192. — Margaritana undulata, Say. 

 Syns. : 



Unio undulatus, Say. 



Alasmodonta undulata, Barnes, Adams. 



Mya undulata, Wood. 



IJnio lirans, Valenc. 



Strophittis sculptilis, Stimp. 



Shell short, tumid, angular behind and widely gaping; breaks 

 prominent, with three or four undulations upon them ; epidermis 

 shining, of a dark olive color, rayed with alternating yellowish and 

 dark bands ; nacre on the anterior half, thickened, opaque, white; 

 on the posterior half, thin, translucent and of a silvery luster, show- 

 ing through it the exterior radiations ; hinge supported on a very 

 strong rib ; the left tooth erect, conical and striated above ; the left 

 tooth erect, and produced backwards under the ligament. Lengthy 

 2 inches; height, If inch; breadth, 1 inch. It is more common 

 than marginata, and is found in the Blackstone River and in most 

 of our larger ponds. 



(To be continued.) 



GENERAL NOTES. 



Species determined. From W. J. Raymond, Oakland, CaL 

 1, Olivella Jioralia Duclos, West Indies ; 2, 0. nivea Gmeliu, West 

 Indies ; 4, Patella confusa Gmel., West Indies. — C. W. J. 



LiMNiEA columella Say. Not found in recent years near Phil- 

 adelphia, is quite abundant in ponds along the line of the Pennsyl- 

 vania Railroad near BonnafFon, Philadelphia. — Ed. 



NatiCxV WANTED. The undersigned wishes to buy, or obtain in 

 exchange, specimens of the genus A'a^tca. John L. Ogden, 72nd st. 

 and Greenway ave., Philadelphia. 



