﻿LAMPSILIS 187 



tends to near the extreme posterior base of the shell, becoming 

 narrower behind, and between it and the posterior opening 

 the two valves touch only for a very short distance. 



Group of Lampsiiis simpsoni. 



vShell long, obovate, gaping in front and behind, rounded at 

 each end ; epidermis dull, rayed when young, dark when adult ; 

 teeth very much reduced ; nacre bluish or purplish. 



Animal unknown. 



lyAMPSims SIMPSONI Ferriss. 



Shell subsolid, elongated, slightly obovate, narrowed in front 

 and rather evenly rounded at both ends, somewhat inflated, 

 having the greatest diameter in the middle and gradually taper- 

 ing each way to the ends, feebly gaping at the anterior base 

 and at the posterior end ; beaks rather low but distinct, their 

 sculpture consisting of ill-defined, irregular, subnodulous cor- 

 rugations ; epidermis in the young projecting beyond the shell 

 all around, showing the uneven growth lines ; color tawny, with 

 green rays and coppery beaks in the young, brownish or black- 

 ish in the adult ; posterior ridge well marked in the earlier 

 stages of growth ; hinge line evenly curved ; pseudocardinals 

 reduced to mere stumpy vestiges ; there are two feeble remote 

 laterals in the left valve and one in the right ; epidermal matter 

 folded in along the hinge line ; anterior cicatrices rather deep, 

 irregular ; posterior cicatrices shallow ; nacre shaded violet, blu- 

 ish and coppery, iridescent behind. I cannot tell whether the 

 specimen figured is a male or female. 



Length 95, height 50, diam. 32 mm. 



Type locality. Spring River, Hardy, Arkansas. 

 Lainpsilis simpsoni Ferriss, Nautilus,. XIV, 1900, p. 38, fig. 



This is perhaps most closely related to L. leptodon and am- 

 phicJurna, though it resembles to some extent L. gracilis. Its 

 teeth are much more feebly developed than those of the latter 

 and it is a longer shell. The young are more like those of 

 .leptodon, but the mature shell is very different from that. 



