cragin.] DESCRIPTIONS OF SPECIES. 77 
ever, is in part due to the orogenic movements which the matrix has 
undergone is indicated both by other variation in the form and by the 
discrepancy sometimes shown in the relative position of the two beaks 
of a single shell. 
Measurements. — Height, 26 mm.; length, 34 mm.; breadth, 21 mm. 
Same dimensions from a left valve, respectively; height, 24 mm.; 
length, 29.5 mm. ; breadth (by doubling the convexity of one valve), 
15 mm. Umbonal fractions, f§, ff, {±, }$. 
Occurrence. — Fourteen specimens were collected from the locality 
\\ miles east of Malone station ; one from the anticline on the eastern 
slope of Malone Mountain nearly 1 mile north of the southern end; 
and one also upward of 1 mile east of Finlay station. 
CYPRINID^]. 
Genus CYPRINA Lamarck. 
Cyprina coteroi C. and A. 
PI. XIII, figs. 11, 12. 
Cyprina (^ 7 cuilia) ceteroi Castillo and Aguilera, 1895, Bol. Com. Geol. Mex., 
No. 1, p. 8, PI. V, figs. 4 to 10. 
Shell thin, triangular-ovate, inequilateral, ventricose, the height 
generally equaling one and a third to nearly one and a half times 
the breadth and about seven -eighths of the length; posterior slope 
flattened and separated from the rest of the shell by a low crest, or 
angulation, which runs from the posterior side of the beaks to the 
somewhat pointed infero-postorior end of the shell; beaks situated 
between the middle and the anterior third, strongly inflated, high 
arched, pyramidal, incurved, somewhat anteriorly deflected, and 
nearly, if not quite, in contact; pallial line entire; general surface 
ornamented with ordinary concentric growth lines and at remote 
intervals with resting stages marked by moderate imbrication and 
groove, which descend across the posterior flattened area and turn 
suddenly forward at the posterior angulation. 
Measurements. — Height, 34 mm.; length, 41 mm.; breadth, 27 
mm. 
Occurrence. — Four (and two doubtful) specimens, from locality 1^ 
miles east of Malone station. 
There is some doubt as to the true horizon of the type specimens of 
this fossil. See remarks as to same on page 72, under Lucina 
potosina. 
