THE NAUTILUS. 47 



Mya rxigulosa, 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, Ito inch ; breadth, tV 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. : 



TJnio undulatus, Say. 

 Alasmodonta undulata, Barnes, Adams. 

 Mya undxdata, Wood. 

 TJnio lirans, Valenc. 

 Strophitus 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. Length, 

 2 inches; height, 1| 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 floral ia Duclos, West Indies ; 2, 0. nivea Gmelin, West 

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



LiMN.EA 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. 



Natica wanted. The undersigned wishes to buy, or obtain in 

 exchange, specimens of the genus iVaftca. John L. Ogden, 72nd st, 

 and Greenway ave., Philadelphia. 



