252 PALEONTOLOGY OF NEW YORK. 



BYSSOPTERIA, Hall. 



Byssopteria radiata. 



PLATE XXXII. FIGS 21, 22; and PLATE LX.XX, FIG. 11. 



Mytt lata, II u.i.. Ms. L877. 



S. A. Mii.i.kk. Cat. Amer. Pal. Fossils. 1877. 



Byssopteria radiata, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 32, figs. 21. 22; 



pi. SO, fig. 11. Jan., 1SS3. 



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 stria? 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. 



