PANDORA. 61 



Ocnus NE.EBA, Gray. 18.34. 



Shell pear-shaped, iiieqiii valve, thin, usually radiatcly rihhcd, 

 heaked and gaping posteally, with an internal rib ; hinge with an 

 oblique ledge, a minute tooth contiguous, and an obsolete lateral 

 tooth ; animal with closed mantle, small crescentic foot ; siphons 

 short, contracted, upper one smallest and with an extensile valve, 

 both with a few long filaments at their sides. 



Nesera pellucida. 



Necera pellucida, Stimpson-, Inv. Gr. Munan, 21, fig. 13 (1853). 



Shell small, thin, ])alo white, sub-ovate, swollen anteally and 

 contracted posteally into a short but distinct rostrum. Beaks small, 

 tumid, and placed a little before the middle. Surface 

 nearly smooth about the beaks, with irregular, distant 

 striae of growth near the margin, which become sharp 

 and well marked on the rostrum. Within smooth and 

 glossy, with minute radiating lines across the disk ; jv. peiiudda. 

 teeth very minute. Epidermis white, sometimes pale 

 greenish on the beaks and brownish on the rostrum. Length, 

 nineteen hundredths of an inch ; height, twelve hundredths of an 

 inch ; width, eleven hundredths of an inch. A specimen from Casco 

 Bay measures length, live tenths of an inch ; breadth, eighteen 

 hundredths of an inch ; height, three tenths of an inch. 



The above description is copied from Dr. Stimpson, who discov- 

 ered this species, the first found on our coast. It resembles N. 

 cuspidata, Forbes and Hanley. It was taken in forty fathoms, on 

 a muddy bottom, off Long Island. Also in a haddock taken near 

 Portland (^Foivler^. 



Family PANDORID^. 



Shells irregular, inequivalve, compressed, pearly ; mantle closed; 

 branchiae of each side coalescing ; siphons separate at tips only. 



Genus PANDORA, Brug. 1792. 



Shell inequivalve, inequipartite, pearly within ; right valve flat, 

 left valve convex ; hinge with two diverging teeth in the flat valve 

 and corresponding grooves in the opposite one. 



