FAMILY MYADZ — PANDORA. 239 
PANDORA TRILINEATA. 
PLATE XXXIII. FIG. 310. a. x. 
(STATE COLLECTION.) 
Pandora trilineata. Say, Jour. Acad. Nat. Sc. Vol. 2, p 261. Ip. Conchology, pl. 2. 
P, id. Conrap, Am. Mar. Conch p. 49, pl. 11, fig. 1. Russet, Ess. Jour. Vol. 1, p. 54. 
Sie id. Goutp, Invertebrata of Mass. p. 44. 
T2h nasuta. Sowerpy, 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 strie 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, 0°45 — 0°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. JLinneus. 
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. Gulls 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. 
