NATURAL SCIENCES OF PHILADELPHIA. 
121 
is another strong one, and still beyond, a very feeble one. None of the shell 
being preserved, no revelations are made of the minute structure. 
Length, *17 (100) ; breadth, ’15 (88) ; thickness, *09 (53). 
Collected by A. Winchell, at Rockford, Indiana. 
The straight beak of the ventral valve, and the general aspect of the shell, 
render the above generic reference unsatisfactory. Externally it seems to 
have some relations with Trematospira and Leptoccelia, of Hall, while it still 
more strikingly resembles Spirifer Buchianus, de Kow, (Anim. Foss. pi. xv. 
bis fig. 3, and xix. fig. 6 ;) but until its internal characters are known, I leave 
it where it stands. 
Rhynchonella heteropsis, n. sp. Shell small, varying from sectoriform to 
transversely elliptic, with moderately projecting beak; very young speci¬ 
mens in the shape of a barley-corn. Plications sharp, ranging in number 
from ten to twenty ; of which three generally (sometimes two or four,) occupy 
the sinus of the ventral valve. This valve has a moderately sharp beak, 
turned back in an angle of 45° with the plane of the shell, and slit (in the 
cast) from the apex to thehingb; sinus deep toward the front of the mature 
shell, wanting in the young one ; the plications on each side of the sinus vari¬ 
able ; four in those with two plications in the sinus, six, seven or eight in 
those with three, and five in those with four, making the whole number of 
plications ten to nineteen. These lateral plications are bent backwards in 
approaching the margin. Greatest prominence of ventral valve near the beak. 
Dorsal valve more ventricose than the ventral, most prominent at the ante¬ 
rior margin ; mesial fold much less marked than the sinus opposite, consist¬ 
ing of two, three, four or five plications, elevated at their extremities some¬ 
what above the lateral plications, the remotest of which exhibit a strong 
downward curvature. Beak of this valve concealed beneath that of its fel¬ 
low. 
Length, *38 (^90) ; breadth, -42 (100) ; thickness of both valves, ’28 (67). 
From one of the calcareous beds, “No. 4,” of the yellow sandstone, Bur¬ 
lington. “ White Collection” of the University of Michigan. Also near Ham¬ 
burg, Illinois, and at Weymouth, Medina county, Ohio. Whittlesey’s Collec¬ 
tion. 
I had hoped that these varying forms could be brought under one of the 
numerous species already described from this group. It is a much smaller 
shell, with more abrupt sinus than R. pustulosa, White, from the same loca¬ 
lity. It is about the size of R. camerifera, Win., from Pt. aux Barques, but, 
besides wanting the long dental and median plate's of that species, the sinus 
and fold are much more strongly marked, and the transverse diameter is re¬ 
latively greater, giving the rostral region less relative prominence; and the 
mean number of plications is considerably less. In the rostral region it dif¬ 
fers from R. Sageriana, Win., in the same manner, besides being a smaller 
shell with shallower sinus. 
Rhynchonella persinuata, n. sp. Shell of medium size, transversely oval, 
with abbreviated rostral extension. Cardinal slopes nearly straight, sides 
rounded, front straight. Ventral valve depressed, with about twenty straight 
plications, of which eight occupy the broad and rather shallow sinus. Ante¬ 
rior margin of valve abruptly deflected. Dental lamellse extending nearly 
one-third the length of the valve. The beak of this valve projects nearly in 
the plane of the shell, and the lateral portions of the valve are continued, 
without convexity, to the borders, thus giving this valve a peculiarly flatten¬ 
ed surface—the broad sinus forming a similar plane lying at a lower level. 
Transverse diameter, -67 (100); length, *52 (77); thickness of ventral 
valve, -16 (24). 
Burlington, Iowa, in the yellow sandstone. “White Collection” of the 
University of Michigan. 
1865 .] 
