LAMELLIBRANCHIA TA. 249 



LlMOPTERA OBSOLETA. 



PLATE XXIX, FIGS. 5, 6; PLATE XXVI. FIG. 10? ; and PLATE XCII. FIG 10. 



Limoptera otsoleta, Hall. Prelim. Notice if Lam. Shells, etc., pt. 2. Dec, 1869. 



" " Pal. N. T., 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. 



Valves 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 stria? 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 stria? 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 

 32 



