252 
PALEONTOLOGY OF NEW YORK. 
BY SSOPTERIA, Hall. 
Byssopteria radiata. 
PLATE XXXII, FIGS. 21, 22; AND PLATE LXXX, FIG. 11. 
Mytilarca radiata, Hall. MS. 1S77. 
“ “ “ S. A. Miller. Cat. Amer. Pal. Fossils. 1877. 
Byssopteria radiata, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 32, figs. 21, 22; 
pi. 80, fig. 11. Jan., 18S3. 
Shell large, wide-triangular, alate posteriorly; body undefined; length about 
five-sevenths of the height; anterior margin vertically truncate the entire 
height of the shell; basal and posterior margins broadly rounded. 
Valves sub-equal, depressed-convex on the basal and post-basal sides, sub- 
angularly gibbous on the umbo and along the anterior side. 
Hinge-line straight, less than the length of the shell. Beaks anterior, 
acute, elevated, and directed forward. Anterior end sub-nasute. 
Test marked by strong, sub-equal, rounded radii which are wider than the 
interspaces, often bifurcating below the middle of their length, and on the 
outer portion of the undefined wing they are fasciculate and finer. Entire 
surface marked by striae of growth which become elevated into fascicles 
toward the margins. 
Interior unknown. 
A right valve has a length of 55 mm. and height 72 mm. A left valve 
measures 54 mm., in length, and 79 mm., in height. 
This species is unlike any Pectinoid or Aviculoid form described in this 
volume, and has somewhat the aspect of several species of Ambonychia from 
the lower rocks, although probably very distinct in its generic relations. 
Formation and locality. In the Upper Chemung group at Mansfield, Tioga 
county, Pa. 
