Morgan Expeditions. 116 
precludes its being placed in the genus Pleurotomaria, to 
which it might seem to be related from the shape and appear- 
ance of the internal mould alone. 
Very abundant in the Devonian sandstone of Ereré, Prov. 
of Para, Brazil; associated with Spirifera Pedroana, Nucu- 
lites Nyssa, etc. 
Dedicated to Mr. Furman of Para, a gentleman to whom 
both expeditions are deeply indebted. 
Genus PLATYCERAS, Conrad. 
Platyceras symmetricum. 
Platyceras symmetricum, Hall. 15th. Ann. Rep. St. Cab., N. Y., 1862, p. 
34. 
Description of the Ereré form:— Shell small, argonautiform in side 
view, very slightly elongated and somewhat laterally compressed. From 
the apex, which is minute and twisted very slightly to-the right of the . 
median line, the shell increases very rapidly in size, the ventral side of 
the body volution passing tangentically for a short distance beyond the 
last preceding volution. Volutions about one and one-half in number, 
the outer one, small and much compressed where it commences, but be- 
coming gradually less compressed and more fully rounded toward the 
aperture, enlarging rapidly at the same time. The aperture is oval in out- 
line, with the sinistro-dextral diameter a little less than the dorso-ventral. 
The margin is apparently sinuous, but is defective in the specimen. Exte- 
rior surface of shell not preserved. Surface of internal mould of body 
volution not very irregular, somewhat rugose and traversed near the front 
by numerous, rather indistinct growth lines, which bear on each side a few 
deep, rounded flexures. To these flexures a few short, irregular, longitu- 
dinal undulations near the aperture appear to correspond. There is a 
slight prominence, probably the impression of the base of a spine, just on 
the left of the dorsal line, midway between the aperture and the beginning 
of the outer volution. Dimensions: greatest length from anterior mar- 
gin of aperture, 19™™; dorso-ventral diameter of aperture, 13.5 ™™; 
sinistro-dextral diameter of same, 12 ™™, 
Only one specimen of Platyceras, the one described above, 
was obtained from Ereré. It agrees with P. symmetricum 
of Hall, Hamilton group, N. Y., in being symmetrical and 
in having the same number and character of volutions ; but 
it is much smaller than any specimen of P. symmetricum 
from the Hamilton group which we have seen, and more per- 
