LAMELLIBRANCHIATA. 499 



Valves depressed-convex in the lower and posterior portion, becoming con- 

 vex in the umbonal region. 



Beaks at about the anterior fifth, small and appressed, rising but little 

 above the hinge-line. Umbonal slope convex above, not defined toward the 

 post-inferior extremity. 



Surface marked by fine concentric striae, which are fasciculate, and pro- 

 duce undulations of the surface at irregular intervals, and are more con- 

 spicuous on the posterior half of the shell. Anterior muscular scar situated 

 just below the lunule, near the anterior extremity. Cardinal margin flat- 

 tened as in other species of this genus. 



Two specimens measure respectively 40 and 51 mm. in length, and 17 and 

 22 mm. in height. 



This species resembles G. depressus, but is distinguished by its greater con- 

 vexity, more elongate form, and much more extended anterior end. 



Formation and locality. In a red sandstone of the Chemung group, at Nelson, 

 Tioga county. Pa. 



Glossites procerus, n. sp. 



PLATE XCVI, FIG. 13. 



Shell above the medium size, elongate-sub-elliptical, narrower in front ; length 

 two and one-half times the height; basal margin gently curved, abruptly 

 rounded into both extremities. Posterior margin recurved to the hinge- 

 line. Cardinal line gently arcuate. Anterior end produced, declining from 

 the be<aks and narrowly rounded in the lower part. 



Valves depressed-convex in the lower and posterior portions, becoming 

 moderately convex along the middle and in the umbonal region. 



Beaks at about the anterior fifth, small and closely appressed. Umbonal 

 slope not strongly defined, but the convexity continues to the post-inferior 

 extremity. 



Surface marked by fine striae of growth, which are sometimes fasciculate, 

 forming concentric undulations. Anterior muscular scar strongly developed. 



