120 GEOLOGICAL SURVEY OF THE TERRITORIES. 
ACTINOZOA. 
Genus AMPLEXUS Sowerby. 
AMPLEXUS ZAPHRENTIFORMIS White. 
Plate 33, figs. 1 a, b, ¢, and d. 
Amplexus zaphrentiformis White, 1876, Powell’s Rep. Geol. Uinta Mts., p. 107. : 
Corallum having the external aspect of Zaphrentis, elongate-conical in 
form, more or less curved and tapering to a point or a Small basal ped- 
icel; epitheca well developed, having its surface marked by the usual 
concentric wrinkles and lines of growth, and with longitudinal lines 
which mark the position of the septa, the latter not being very distinct; 
calyx circular or subcireular, the plain portion of the surface at its bot- 
tom equal to one-third or more of the diameter of its rim; septal fosset 
well developed, usually situated at the concave side of the corallum, 
but not always; septa thirty or forty in number, rather strong; trans- 
verse plates numerous, well developed, somewhat irregular in direction, 
as well as in their distance apart, and ending exteriorly against a mod- 
erately well developed external wall, which is distinet from or of greater 
thickness than the epitheca proper. This external wall apparently con- 
tains no vesicles, but appears to consist of solid coralline substance. 
The largest example in the collection is about ninety millimeters in 
length, the calyx having a diameter of twenty-five millimeters; but the 
average size of the nearly one hundred examples in the collection is con- 
siderably less. 
This differs from all other American species of Amplexus known to me, 
in its zaphrentoid form; but its plain calyx-bottom, its broad trans- 
verse plates, and the absence of a vesicular zone, leave no doubt as 
to the propriety of referring it to the genus Amplexus. Although the 
corallum is somewhat stronger, proportionally shorter, and its sides less 
nearly parallel than is usual with Amplexus, it is not proportionally so 
short as that of A. henslowi Edwards & Haine, from the Carbonifer- 
our rocks of Belgium. That species, according to those authors, has a 
compact, massive form, six centimeters in height, and a diameter of 
calyx equal to four or five centimeters. Our species may be compared 
with this, as to the zaphrentoid form of both, but the differences be- 
tween them in other respects are too great to need comparison as to spe- 
cifie identity. 
Position and locality.x—This species has yet been discovered only in 
the Uinta Mountain region. All the examples in the collection were 
collected by Professor Powell from the middle division of the Carbonif- 
erous series, designated by him as the Lower Aubrey Group, in Split 
Mountain Cafion, and near Echo Park, Green River, where that stream 
traverses the Uinta Mountain chain. 
Genus ACERVULARIA Schweigger. 
ACERVULARIA ADJUNCTIVA White. 
Plate 35, figs. 1 a, b, c, and d. 
Acervularia adjunctiva White, May, 1880, Proc. U. S. National Museum, vol. ii, p. 255. 
_Corallum massive or subdiscoidal, composed of compactly united cor- 
allites of somewhat unequal size; corallites approximately straight, 
