cragin.] DESCRIPTIONS OF SPECIES. 101 
| a region of maximum, yet moderate inflation, near the umbilicus to 
the rather narrowly rounded periphery; septa about 24 to each turn, 
the sutures feebly waved or sigmoid ; umbilicus narrow, filled with a 
shelly columella; surface of shell smooth. The position of the 
isiphuncle has not been determined. 
Measurements. — The greatest diameter of the larger specimen is 
about 122 mm. The height of the largest preserved part of the body- 
I chamber in its median plane is about 50 mm. The height of the 
same part of the body-chamber over all, or measured on a tangenl <<> 
the flank from the level of its umbilical border to the level of the 
'periphery, is about 71 mm. (66 on one flank, 70 on the other flank, 
j in the specimen as preserved, the umbilical axis having an oblique 
position, due to crushing). The original breadth of the same part of 
the body chamber, allowing for crushing, was apparently not less 
| than 60 mm. 
Occurrence. — Two imperfect specimens of this shell were collected 
by Doctor Stanton in foothills near the railroad, at the northwest 
end of Malone Mountain, about 2 miles east-southeast from Finlay 
station, the horizon not more than 200 feet above the gypsum bed. 
AMMONOIDEA. 
Genus OPPELIA Waagen. 
Oppelia ? fallax (C. and A.). 
PI. XXII, figs. 2, 3. 
Placenticeras fallax Castillo and Aguilera, 1895, Bol. Com. Geol. Mex., No. I, 
p. 17, PI. VIII, figs. 1, 2. 
IThis large, plain, compressed, and obtusely lenticular ammonite is 
rather common in the limestone portions of Theta subdivision of the 
Trio section, H miles east of Malone station, but has been obtained 
thence in fragmentary specimens only. 
The following is a translation of the original specific description : 
1 
Shell compressed, narrowly nmbilicate. Spire composed of not very numerous 
embracing whorls, which almost completely hide the previous whorls. Flanks 
feebly convex, descending gradually toward the umbilical border and with the 
same regularity toward the siphonal region, which is rounded and a little more 
narrow than the flanks ; the greatest thickness of the shell is on the umbilical 
border. Umbilicus very narrow and deep, with vertical walls, with uncari- 
nated border. Aperture very high, considerably invaded by the spire whorl, 
rounded in the upper part, of nearly elliptical form. Surface of the shell 
smooth on the last whorls, bearing in the earlier whorls fine lines of growth. 
Diameter, 104 nun.; breadth of the last whorl in relation to the diameter, 0.54; 
thickness of the last whorl in relation to the diameter, 0.32; diameter of the 
umbilicus in relation to the diameter. 0.10. 
