62 PANDORID.E. 



Pandora trilineata. 



Shell oblong-ovate, rounded before, and with a recurved beak behind. Along- 

 the posterior hinge margin of both valves run two rough, elevated, radiating 

 lines. 



Pandora triUiifata, Say, Jonrn. Acad. Nat. Sc. ii. 261 ; Amcr. Conch, pi. 2. — Conrad, 

 Amer. Mar. Conch. 49, pi. 11, tiR. 1. — Lam., An. sans Vert. vi. 147. — De Kay, 

 Nat. Hist. New York, 239, pi. 33, fig. 310. — Stimpson, Shells of New England, 

 23. — MiGUELS, Catal. Shells of Maine, 8, and Best. Journ. Nat. Hist. 



Pandora nasuta, Sowerby, Species Conch, figs. 18, 19. 



Shell pearly-wliitc, ovate, iiiequipartitc, the anterior part liigli and 

 regularly rounded, about half the length of the posterior part, which 

 has the hinge margined, flattened, straight or somewhat concave, 



the edge of the flat valve shutting 



Fi*^ 379 



over the edge of the convex valve, 



and terminating in a recurved or 



\1^V^ /^m' \\'^\N'y^!/ ascending tip, its points coarsely 



wrinkled, irregular, and slightly 

 gaping ; the anterior ]:)ortion of the 



p. trilineata. t? J & ' _ i 



basal margin has a depending or 

 pouch-like appearance ; the upper edge is margined by two wrin- 

 kled, rounded lines radiating from the Ijcaks, most obvious on the 

 convex valve ; surface wrinkled with undulating lines of growth, 

 and with very faint radiating lines on the flat valve ; sometimes 

 there is a slightly impressed line passing from the beak to the 

 middle of the base, and in fresh specimens the portion anterior to 

 this line has a sort of mud-colored epidermis as if the shell had 

 been forced into the mud endwise up to this line. Hinge in the 

 left or convex valve with three diverging teeth, the anterior one 

 much the longest and strongest, the middle one very delicate ; the 

 third is rather a thickening of the posterior margin, with a ledge 

 in it for the reception of a tooth in the opposite valve. Right or 

 flat valve with two teeth, one short, triangular, strong, directed 

 across the shell, the other long, inclined to the posterior hinge 

 margin. Within iridescent ; muscular impressions rounded, con- 

 nected by a series of about a dozen rough spots for the adhesion 

 of the mantle. Length, one and three tenths inches ; heiglit, 

 seven tenths of an inch ; breadth, one fifth of an inch, nearly. 



The animal has the mantle closed except for the issue of the 

 slender foot and the siphons ; branchige continued Avithin the si- 

 phon, and coalescing posteriorly ; siphons short, purplish, the up- 



