G04 Systematic Paleoxtology — Upper Devonian 



Family ATHYRIDAE 



Genus ATHYRIS McCoy 

 AtHYRIS ANGELICA Hall 



Plate LIX, Figs. 8-10 



Athyris angelica Hall, 1861, 14th Kept. N. Y. State Cab. Nat. Hist., p. 99. 

 Athyris angelica Hall, 1867, Pal. of N. Y., vol. iv, p. 292, pi. xlvli, figs. 9-20. 



Description. — "Shell ovoid, gibbous, transverse or elongate; propor- 

 tions of length and width variable, the prevailing form longer than wide ; 

 deeply sinuate, with the beak very prominent; hinge-line short. 



"Ventral valve gibbous, most convex above the middle; mesial sinus 

 usually extending nearly to the beak, becoming abruptly and deeply de- 

 pressed below the middle, and much expanded towards the front of the 

 shell ; lateral portions of the valve gibbous, and abruptly curving towards 

 the ihargins; beak much elevated and curved over the umbo of the dorsal 

 valve. 



" Dorsal valve much shorter than the opposite, gibbous, transverse or as 

 long as wide; the mesial fold usually not conspicuous above the lower 

 third of the valve ; in the upper part the surface is a little more gibbous, 

 and the strife along this part are more straight or a little curved back- 

 wanl?, indicating the form during the successive stages of growth. 



" Surface marked by regular equidistant imbricating lamellae or lamel- 

 liform striae, the edges of which in perfect specimens are projecting and 

 slightly crenulate. These lamellae are marked by short interrupted 

 radiating striae. 



" The interior of the ventral valve shoAvs a semicircular perforation at 

 the apex, opening on the lower side to a triangular fissure. The teeth 

 are strong, and continued in plates to the base of the rostral cavity, and 

 divaricator imprints occupy an ovate space below and on each side. Sur- 

 face of cast, adjacent to the muscular imprints, strongly papillose. 



" The muscular imprints of the dorsal valve are not well preserved in 

 any specimens in my collection. Tliere is a slender longitudinal septum 



