LAMELLIBRANCHIA TA. 
249 
Limoptera obsoleta. 
PLATE XXIX, FIGS. 5, 6; PLATE XXVI, FIG. 10 ? ; and PLATE XCII, FIG. 10. 
Limoptera olsoleta, Hall. Prelim. Notice of Lam. Shells, etc., pt. 2. Dec., 1869. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 29, figs. 5, 6. Jan., 1883. 
Shell large; body ovate, erect or slightly oblique; height greater than the 
length; basal margin regularly rounded; anterior side broadly convex and 
contracting to the byssal sinus; posterior side abruptly recurved from the 
base, and extending in a nearly direct or slightly concave line to the extremity 
of the wing. 
Yalves very unequal. The right valve much depressed or nearly flat; the 
left valve depressed-convex below, regularly convex in the middle, and 
gibbous in the umbonal region. 
Hinge-line straight, nearly rectangular to the axis of the body of the 
shell, less than the length of the valve. 
Beak of left valve prominent, acute, inclined forward, situated anterior to 
the middle of the body, rising much above the beak of the right valve, and 
arching over the cardinal line. Umbonal region prominent, and sometimes 
gibbous, limited anteriorly by a distinct broad depression, and posteriorly by 
the abrupt umbonal slope; subtending an acute angle. 
Ear small, limited by the byssal sinus. Wing moderately large, triangular, 
extending below the middle of the length of the body; extremity abruptly 
rounded. 
Test thick, marked by irregular concentric striae of growth, which are 
crowded and strongly lamellose on the lower half of the body and on the 
anterior and posterior sides. On the wing, just below the cardinal line, the 
striae turn gently outward. In some specimens there remain obscure indica¬ 
tions of radii. 
Ligamental area wide, extending the entire length of the hinge-line; 
marked by coarse undulating striae and wider intermediate grooves. Other 
characters of the hinge and interior not observed. 
One of the specimens figured has a height of 88 mm., and another of 100 
T2 
