198 PALEONTOLOGY OF KENTUCKY. 



sub-quadrate in outline, strongly alate on the posterior side, and often more or 

 less produced on the anterior end. The valves are convex in all species known ; 

 the left valve being strongly convex throughout, while the opposite one is but 

 slightly elevated, and in one species is somewhat concave near the base. The 

 surface is coarsely radiate in all but one species. The ligamental area is large, 

 in both valves sub-equal, and without cartilage pits. Lima macroptera of 

 Conrad may be considered as type of this genus. 



Limoptera cancellata. HALL. 



Plate III., figures 6, 7 and 8; Plate IV., figure 24. 

 Limoptera cancellata, Hall. Prel. Nat. Lam. Shells, pt. 2 1869. 

 Limoptera cancellata, var. occidens, H. and W. 24th Reg. Rep., p. 199 1872. 

 Limoptera cancellata, Hall. Pal. N. Y., Vol. 5, pt. 1, p. 2441883. 



Shell large ; body sub-erect ; general outline very variable, from broadly 

 ovate to sub-elliptical ; axis of the body nearly vertical to the hinge-line ; pro- 

 portion of height to length very variable ; sometimes both dimensions are nearly 

 equal, but mostly the height predominates over the length, and, as shown in 

 our illustration, in some shells to a considerable extent. The prevailing form 

 may be described as follows : Elongate oviform, almost erect, with a slight 

 anterior inclination ; plano-convex, with the left valve strongly convex in the 

 umbonal region, and only moderately convex, almost flattened, in its basal 

 half. The right valve is entirely flat, with only a gentle elevation in the 

 umbonal region. Height exceeding the length ; their proportion as four to 

 three. 



The margins in the lower or basal half of the shell regularly curved ; in the 

 upper half, the anterior margin of the body is only slightly rounded, while 

 the posterior margin of the body forms an entire straight line. 



The lateral slopes of the umbonal region are very steep, meeting the surface 

 of the wings almost at right-angles, forming thus a demarcation line for the 

 ears. The wings are unequal, the anterior considerably smaller than the 

 posterior. The front wing forms only a small triangular deflection of the 

 anterior margin, while the posterior wing has a considerable width on the 

 hinge-line, and in its longitudinal dimension extends below the middle of the 

 shell. The hinge-line is usually straight, but sometimes deflected in different 

 directions, as our illustration shows ; it is shorter than the height or length. 

 The umbo of the left valve is prominent, and the beak straight, rounded and 

 pointed, and overreaching a small triangular hinge-area, which has no fora- 

 men. The beak is situated about one-third the length of the cardinal line 

 from its anterior end, and has a decided anterior direction. In the right valve 

 the beak does not extend beyond the cardinal line. The posterior margin of 



