PRODUCTELLiE OF THE CHEMUNG GROUP. 
109 
Productella feoyiiii 
PLATE XXIV. 
Produdus boydii : Hall in Tenth Report on the State Cabinet, p. 179. 1857. 
Shell of medium size or larger, transverse, varying from semielliptical 
to broad-oval from the rounding of the cardinal extremities; cardinal 
line less than the width of the shell. 
Ventral valve varying from moderately convex to gibbous in the middle 
and towards the umbo, with a more or less* defined mesial depression 
extending from the umbo to the front of the shell, which is sinuate, 
somewhat gently curving to the front and baso-lateral margins, abruptly 
depressed on the cardino-lateral slopes, and extended into wide ears 
which are more or less distinctly rounded at the extremities. 
Dorsal valve moderately concave, with a distinct longitudinal mesial 
elevation corresponding to the depression of the ventral valve, and 
giving the basal margin a sinuate outline. Cardinal extremities round¬ 
ed, and the cardinal line much shorter than the width of the shell. 
Surface concentrically striated, and marked by numerous elongate pus- 
tuliform spiniferous ridges supporting slender elongate spines, while 
there are one or two rows of stronger curving spines on the ears. The 
interior of the dorsal valve is marked in like manner by pustuliform 
nodes, indicating fossets on the exterior surface, which sometimes 
have their length transverse to the shell, or producing short transverse 
wrinkles. In some specimens, faint radiating strise mark the surface of 
the shell. 
The casts of the ventral valve show the marks of the occlusor mus¬ 
cles near the apex on each side of the mesial depression, which, on the 
interior of the shell, would be an elevated ridge. The divaricator muscu¬ 
lar impressions are deeply striated, wide and spreading, extending nearly 
to the middle of the length of the shell. The interior of the dorsal valve 
shows a narrow mesial septum, but the cardinal process has not been 
determined. The whole interior surface is papillose or punctate. 
[ Palaeontology IV.] 22 
