PRODUCTELLiE OP THE CHEMUNG GROUP. 
173 
The interior of the valve is finely papillose and papillose-striate, so 
that some of the casts have a minutely interruptedly-striate surface. 
The cast of the ventral valve preserves irregular and somewhat elongate 
semioval imprints of the occlusor muscles, and the impressions of the 
divaricator muscles are deeply striated, wide spreading, reaching the 
inner margin of the wings, and extending for more than one-third the 
length of the valve. The cardinal process of the dorsal valve is bilobed 
in the middle, and each lobe is again divided, leaving a quadruple imprint 
on the stone. 
This shell is subject to much variation in the.convexity of the ventral 
valve, and also in the distribution of the spiniferous tubercles. The larger 
number of specimens are ventricose, a little flattened and rarely depres¬ 
sed along the middle. 
Mr. Conrad has described the ventral valve of S. lackrymosa as '*♦ ventricose, 
“ depressed towards the hinge-extremities; disc slightly flattened in the mid- 
“ die, marked with numerous elongated tubercles arranged in radii which 
“ profoundly bifurcate; hinge-line not salient at the extremities, angulated, • 
“ sub-margin with prominent tubercles; umbo ventricose; summit above the 
“ cardinal line. Locality : Chemung-narrows, New-York, Devonian shale.” 
The specimens in my collections from the Chemung-narrows are usually not 
extremely ventricose, and the spiniferous tubercles are more elongate than in 
most other species in the collection, sometimes becoming costae towards the 
front of the shell. This feature is shown in some of the figures on Plate xxv, 
while other figures illustrate the prevailing forms of those which I have Referred to 
this species from Cattaraugus county and farther west. 
Notwithstanding the variable character of the species, it is for the most part 
readily recognized among the others of the group ; and it certainly has no very 
close resemblance to any of the forms in the Corniferous limestone or Hamilton 
group. / 
The casts show faint indications of an area, and of teeth in the ventral valve; 
but teeth : sockets are not visible in the dorsal valves of any specimens I have 
thus far examined. 
Geological formation and localities. In the Chemung group, near Pactoryville 
and Chemung-narrows, Chemung county; at Painted-post, and near Bath in Steu¬ 
ben county; near Conewango and Randolph in Cattaraugus county, and near 
Ellington in Chautauqua county. 
