366 PALEOZOIC PALEONTOLOGY. 
STROPHEODONTA PERPLANA (Con.). 
Plate LI., Figs. 12-13. 
1867. Strophodonta perplana Hall, Pal. N. Y., vol. IV., p. 98, pl. 
11, fig. 22, pl., 12, figs. 13-15, pl. 17, figs. 1 a-0. 
Description.—Shell subsemi-elliptical in outline, the hinge-line 
usually equaling, but sometimes a little less than, the greatest width 
of the shell; cardinal extremities angular, proportional length and 
breadth variable; lateral margins often more or less sinuate im- 
mediately in front of the cardinal angles. Pedicle valve depressed- 
convex on the umbo, nearly flat towards the lateral and anterior 
margins; beak scarcely projecting beyond the hinge-line; cardinal 
area narrow, linear. Brachial valve nearly flat, leaving but a very 
narrow interspace between the two valves. Surface of both valves 
marked by fine, subequal, radiating coste, which increase by bifur- 
cation and by intercalation, those of the pedicle valve being somewhat 
finer than those of the brachial valve. 
The approximate dimensions of a very imperfect specimen are: 
length, 12 mm.; width, 20 mm. 
Remarks.—The only specimens of this species which have been ob- 
served in the Onondaga limestone of New Jersey are considerably 
smaller than the average size of the species as it usually occurs in the 
Middle Devonian faunas of New York and the west. The specimens 
are very imperfect and scarcely serve to illustrate the characters of 
the species. 
LEPTAENA RHOMBOIDALIS (Wilck). 
Plate LI., Fig. 19. 
See, also, pp. 228, 278, 302, 325. 
Specimens of this widely-distributed species, not unlike those in 
the older formations, are not infrequently met with in the Onondaga 
limestone. 
