PELECYPODA—PRIONODESMACEA 



427 



vex, with arched and incurved beak twisted backward. Right 

 valve depressed-convex, appearing like the operculum of the larger 

 valve ; this valve expands into a small posterior wing. Devonic. 



175. L. laevis Freeh. (Fig. 557.) Devonic. 



Surface marked only with concentric striae. 

 Portage (Naples fauna) of New York. 



Fig. 557. Loxopteria Icevis, right valve 

 (upper), X 2 5 le ft valve, X l S- (After 

 Clarke, Mem. 6, N. Y. State Surv. ) 



Fig. 558. Loxopteria dispar, left valve 

 (upper), X ! -5 '» right valve, X 2 - (After 

 Clarke, Mem. 6, N. V. State Surv. ) 



176. L. dispar (Sandberger). (Fig. 558.) Devonic. 



Surface marked with few radiating ribs but with very numerous 

 and fine radiating and concentric striae. 



Portage (Naples fauna) of New York. 



LI. Lunulicardium Munster. 



Usually triangular, with acute and abruptly terminal, posteriorly 



turned beaks. Shell usually obliquely truncate in front, with a 



deeply impressed area posterior to the beaks ; in this area, between 



the two valves, is a conspicuous opening for the byssus. Posterior 



