ckagin.] DESCKIPTIONS OF SPECIES. 49 
either of which there proceeds to the posterior part of the basal mar- 
gin a low, broadly rounded, umbonal swell, below which in the inter- 
mediate region the flanks are concave; surface nearly plain, marked 
only with ordinary growth lines, some of which are imbricated. 
Measurements. — Height across umbonal region, 11 mm.; same at 
highest section of the shell, 12.5 mm.; length, 37.5 mm.; breadth, 11 
mm. Another example attains a length of 43 mm. 
Occurrence. — The type is from locality li miles east of Malone sta- 
tion, which has yielded two other specimens. I have found a single 
example also, associated with Pleuromya inconstans, Astarte malo- 
nensis, Exogyra mbplicifera /, Gryphma mexicana, and Serpula 
gordialis, at the eastern base of Malone Mountain, in the transverse 
anticline 1 mile from its southern end, just above conglomerates. 
Two additional specimens were obtained by Doctor Stanton, one from 
the anticline just mentioned and one from about 1 mile east of Finlay 
station. 
MODIOLA GENICULATA Sp. n. 
PI. VI, fig. 3. 
Shell small among its congeners, much shorter and higher relative 
to its breadth than M. maloniana, geniculate-trapezoid, the vertically 
expanded posterior half of the shell being rather suddenly deflected 
downward and backward so that its axis makes an angle of about 45° 
with the horizontal cardinal border of the vertically smaller anterior 
half; breadth less than the height, greatest about the middle; beaks 
moderately raised, little inflated; flanks concave in the mid region 
below the umbonal convexity; surface apparently marked only with 
the ordinary growth lines. 
Measurements. — Height, 16 mm.; height of section across middle, 
12.5 mm.; length, 25.5 mm.; breadth, estimated from convexity of one 
valve, 10 mm. 
Occurrence. — A single left valve was collected by Doctor Stanton 
about 1 mile east of Finlay station. 
PINNID^. 
Genus PINNA Linnaeus. 
PlNNA QUADRIFEONS Sp. 11. 
PI. VII, figs. 1-8. 
Shell of medium size in its genus, elongate-cuneate ; anterior region 
nflated, in cross section bicuspidately round-oval to quadrate-oval; 
posterior region rather compressed, in cross section nearly rhombic; 
valves meeting by their ventral margins at an acute and more or less 
compressed or cariniform angle and by their dorsal margins at a 
somewhat similar angle; from their anterior, more convex part, be- 
Bull. 266—05 M 4 
■ 
\ 
