110 GEOLOGICAL SURVEY OF THE TERRITORIES. 
indicate its place in that genus, to which it is provisionally referred, to- 
gether with the two following species, which are all evidently congenerie. 
Position and locality. —Triassic strata; member C of. the foregoing 
section at locality No. 1, Southeastern Idaho. Collected by Dr. Peale. 
AVICULOPECTEN? ALTUS White. 
Plate 32, fig. 3a. 
Aviculopecten altus White, 1879, Bull. U. 8. Geol. Sur. Terr., vol. v, p. 110. 
Shell, exclusive of the ears, subovate in marginal outline; axis almost 
perpendicular to the hinge-margin, or having a very slight forward obli- 
quity ; hinge-margin shorter than the greatest transverse diameter ofthe 
body of the shell. Left valve depressed-convex, the convexity being 
nearly uniform in all parts, except the umbonal region, where itis, as usual, 
greatest; beak small, moderately narrow, pointed, and projecting very 
slightly ‘above the hinge-margin ; posterior ear moderately large, its 
posterior point extending about as far backward as the body of the 
shell, not very distinctly separated from the body of the shell, its pos- 
terior border broadly and not deeply notched; hinder margin nearly 
straight from the shallow notch of the posterior ear to a point a little 
below the mid-height of the shell, from which point the margin is 
rounded with considerable regularity to the anterior side; from that 
side to the base of the anterior ear the margin is a little more abruptly 
rounded ; outer margin of the anterior ear apparently forming a nearly 
right angle with the hinge-margin. Anterior ear apparently small, dis- 
tinct from the body of the shell, but not separated from it by an auric- 
ular furrow. Surface marked by numerous radiating lines and cost, 
which are somewhat irregulariy undulating in their direction ; the latter, 
being more numerous than the lines, the two differing from each other only 
in size. The surface of the anterior ear is faintly marked by numerous 
fine radiating raised lines, but that of the posterior ear is apparently 
marked only by fine lines of growth. Crossing the radiating lines and 
coste there are concentric lines and wrinkles of growth. Right valve 
and hinge unknown. 
Height from base to beak, 55 millimeters; antero-posterior diameter, 
43 millimeters; length of hinge- -margin, 28 nrillimeters. 
This species is congeneric with, and bears considerable resemblance 
to, A. pealer, just described, but it differs from that form in its much 
greater proportionate height, its ana perpendicular axis, its shorter 
hinge-margin, smaller anterior ear,* and in having the heavier radiating 
lines or costes more numerous in proportion to the smaller lines. 
Position and locality.—Triassic strata, Southeastern Idaho, where Dr. 
Peale collected it from locality No. 3, mentioned on a previous page of 
this article. 
AVICULOPECTEN ? IDAHOENSIS Meek. 
Plate 32, fig. 2 a. 
Aviculopecten (Pseudomonotis ?) idahoensis, Meek, 1872, An. Rep. U. 8. Geol. Sur. Terr. 
for 1871, p. 374. 
Associated with the species last described, and also with other forms 
in members A and B of the section at locality No. 1, Dr. Peale found a 
* The condition of the only example discovered would not allow of an entirely sat- 
isfactory determination of the character of the anterior ear, but it is doubtless as rep- 
resented by the artist in plate 32, fig.3 a. The slight for ward obliquity, if it be such, 
makes it somewhat doubtful whether it is really a » left valve, as its other character- 
istics indicate it to be. 
