334 PALEOZOIC PALEONTOLOGY. 
mm. The specimen may represent a new species, but is altogether too 
imperfect for description. The only surface markings to be detected 
are concentric lines of growth. 
GONIOPHORA ? sp. undet. 
A single fragment which seems to be a portion of a small pelecypod 
shell of the genus Gontophora has been observed in the fauna of the 
“trilobite bed.” Even the generic identification, however, is subject 
to much uncertainty. 
GASTROPODA. 
PLATYOSTOMA NEARPASSI Nl. Sp. 
Plate XLIIL., Figs. 1-4. 
Description.—Shell more or less subglobular in form, consisting of 
three or four volutions. Spire low, but little elevated above the outer 
yolution; suture becoming deeply and abruptly impressed as it ap- 
proaches the aperture. Aperture slightly oblique, subcircular in out- 
line, its margin entire, inner lip free below, leaving a narrow, deep 
umbilicus. Surface marked by fine, regular, crowded lines of growth, 
which are sharply raised from the general surface of the shell: 
The dimensions of an average specimen are: maximum diameter, 
10 mm.; height, ? mm. The largest specimen observed has a maxi- 
mum diameter of 14 mm. 
Remarks.—In its general form and proportions this little species 
resembles P. ventricosa and P. desmatum of the higher beds, but may 
be distinguished from either one or both of them by its smaller size, 
its regular, sharply-elevated lines of growth, the absence of revolving 
lines and the abruptly-impressed suture in the younger portion of the 
shell. The species was formerly provisionally identified as a small 
form of Strophostylus transversus Hall, but the inner lip of the aper- 
ture proves to be entirely different from that species. 
