family myad.e — pandora. 239 



Pandora trilineata. 



PLATE XXXIII. FIG. 310. a. b. 



(STATE COLLECTION.) 



Pandora trilineata. Say, Jour. Acad. Nat. Sc. Vol. 2, p 261. Id. Conchology, pi. 2. 



P. id. Conrad, Am. Mar. Conch, p. 49, pi. 11, fig. 1. RuesEL, Ess. Jour. Vol. 1, p. 54. 



P. id. Gould, Invertcbrata of Mass. p. 44. 



P. namta. Sowerby, fig. 18 - 19. 



Description. Shell irregularly wedge-shaped, rounded before, with a recurved subtruncated 

 beak behind. Hinge-margin with a concave curve ; the surface above flattened, and bounded 

 on its edges by two elevated lines from the beaks to the rostrated tips ; anterior portion of the 

 basal margin strongly curved. Surface with fine undulated incremental striae and faint ra- 

 diating lines ; rostrated portion coarsely wrinkled and gaping. Three or more distinct lines 

 radiate from the beaks. The flat valve with two teeth, of which one is shorter and more 

 robust than the other ; the cavities in the other valve, to receive these teeth, exhibit between 

 them the appearance of three teeth or teeth-like elevations. 



Color. Pearly white ; within, bluish iridescent. 



Vertical axis, - 45 - - 6 ; transverse ditto, 0*9 — 1*2. Diameter, 0"2. 



This delicate and singular species occurs on our coast from Maine to Florida. It is found 

 along the shores of Long island and Staten island. On the coast of the latter island it is very 

 commonly washed ashore, attached to seaweed. Here its locality is limited to a small spot 

 at the foot of Coverly's lane, on the south side. In the more perfect and larger specimens, 

 a fourth oblique line may be traced between the two approximated hinge-marginal lines and 

 the third oblique one. In many specimens, a byssus associated with sertularia. is attached 

 to the beaks. 



GENUS MYA. Linnceus. 



Animal with a moderately thin mantle, adhering by its edges, closed by a membranous plate, 

 and forming behind around its tubes a loose membranous envelope into which it is retracted . 

 Tubes united, slightly separated at their summits, and radiated at the orifices. Foot very 

 small, coming out from the mantle by a small slit at the antero-inferior portion in the me- 

 dian line. Gills moderate, unequal, on the same side. Mouth small, with triangular 

 striated appendices. Shell moderately thin, transverse, gaping at both ends, with an epi- 

 dermis. Left valve with a single broad compressed upright tooth, received into a pit of 

 the -opposite valve. 



