34 
Schuchertella girtyi n. sp. 
Plate I, figures la-c 
1900. Orthothetes chemungensis var. Girty, U.S. Geol. Surv., 20th Ann. 
Rept., pt. 2, p. 40, PI. 3, figs. 4-6; Schuchertella chemungensis 
Kindle, 1909, U.S. Geol. Surv., Bull. 391, p. 16, PI. 3, figs. 2-4a. 
Description . Shell small, biconvex, wider than long, with hinge-line 
apparently shorter than the greatest width of the shell. Delthyrium 
slightly higher than wide. The dimensions of a somewhat imperfect shell 
are: length of pedicle valve 19 mm., of brachial valve 16 mm.; greatest 
breadth (apparently near the mid-length of the shell) 24 mm. + ; thickness 
9 • 5 mm. ; length of hinge-line 19 mm. + ; length and basal breadth of del- 
thyrium 5*5 mm. and 4*5 mm. A smaller pedicle valve was 13 mm. long 
and 17 mm. wide. 
Pedicle valve arched from beak to front, distinctly so in the umbonal 
region, very slightly so or almost flat beyond. Transversely the valve is 
most convex in the umbonal region, from the highest point of which the 
valve descends in almost straight lines to the cardinal margin. Anteriorly 
the valve is slightly flattened medially. Cardinal area high, transversely 
and vertically striate, straight below, arched above, the lower part in- 
clined posteriorly so as to form an angle of about 110 degrees with the 
plane of the junction of the two valves. Beak twisted, projecting slightly 
over the cardinal area. Delthyrium covered by a convex, transversely 
ridged, and striated deltidium. Internally, both dental lamellae and 
median septum absent. 
Brachial valve very gently and subequally convex both longitudinally 
and transversely. Cardinal area very narrow. 
Surface of both valves marked by fine, rather sharply elevated radial 
costae, about 12 to 16 of which occupy the space of 5 mm.; interspaces 
wider than the costae. These costae may be nearly equal in height and 
breadth, may alternate in size, or each third or fifth costa may be con- 
siderably stronger than the intermediate ones. Fine concentric growth 
lines are faintly visible between the striae. 
Remarks. Our form is apparently identical with the one described by 
Girty from the Ouray of Colorado under the name of Orthothetes chem- 
ungensis var. 1 Girty finds this variety variable in convexity of pedicle and 
brachial valves, the height of the cardinal area, and the length of the 
hinge-line, which may be either shorter or considerably longer than the 
width of the shell below. In our specimens the hinge-line is apparently 
always shorter. The surface striae Girty finds as variable as in our speci- 
mens. S. chemungensis Conrad is a much larger shell, with stronger 
costae. Generically, this species is referred to Schuchertella Girty, for, 
though the beak is twisted, this torsion does not extend to the broader 
umbonal region as in Streptorhynchus King. The genotype of Schuchertella, 
S. lens , has the beak distorted about as much as has this species. In 
Streptorhynchus , likewise, the cardinal area is usually high and narrow. 
Locality and Horizon. In the Upper Devonian (Ouray) of Colorado. 
In the Minnewanka region in the Upper Devonian of section 2-38 (r). 
*Loc.cit. 
