178 Cincinnati Society of Natural History. 
and much better defined at the anterior end; very narrow at the 
ventral edge. Valves rather tumid at and below the center; 
anterior and ventral slopes abrupt, the posterior slope more gentle. 
Central portion of dorsal slope a little depressed, with a broad and 
low swelling on each side. ‘The latter with a small tubercle near’ 
the center of the dorsal edge and a pair of similar ones situated 
near the antero-dorsal angle, have suggested the name sudbnodosa. 
Surface finely pitted. 
This species is more elongate, has a wider, though illy defined, 
flattened posterior border, and more uneven surface than any other 
species of the genus known to me. 
Position and locality: Upper Trenton limestone, associated with 
Leperaitia linneyt, at Perryville, Ky. 
ISOCHILINA SAFFORDI, N. Sp. 
TAGE LA, SUES ORD ON CC 
cee Smallright valve; length, 5.0mm.; height, 3.2mm. 
Large left valve ; ShU'e LO Zee <> 9.6 “* thickness; 4.0 mm: 
Carapace large, oblong, elliptical, with the ends subequal, semi- 
circular; dorsal margin straight or slightly convex, curving neatly 
into the posterior edge, but anteriorly terminating with a short 
spine-like prolongation. Flange sharply defined, wide at the ends 
(the most so at the posterior) and very narrow at the ventral side. 
Body of valve with point of greatest convexity in front of and 
somewhat beneath the center; from here the slope of the surface 
is flattened to the beginning of the flange where the descent is 
rather abrupt. Muscle spot distinguishable, situated just above 
the point of greatest convexity. Eye tubercle distinct. Surface 
with faint reticulating granulose lines. 
This species is related more or less closely to a number of forms 
—chiefly European; but is distinguished by the peculiar surface 
ornamentation, the rounded character of the postero-dorsal edge, 
and other less obvious features. 
The specific name is given as a small compliment to Prof. J. M. 
Safford, the State geologist of Tennessee, who, in his work on the 
geology of that State, did not overlook even this so generally 
neglected class of fossils. 
Position and locality: Upper Trenton limestone, Nashville, 
Tenn. ‘The specimens are a glossy black, and occur in a compact, 
dark gray limestone. 
