138 GEOLOGICAL SURVEY OF THE TERRITORIES. 
genus, although it corresponds in all essential respects with the generic 
diagnosis given by Professor King. It is evidently congeneric with the 
species described by Meek in the final report on the geology of Ne- 
braska, p. 217, pl. x, fig. 15, under the name Allorisma (Sedgwickia) 
refleca. That species is from the Upper Coal-measure strata at Nebraska 
City, Nebr., and it has also been found in the Lower Coal-measures 
of Illinois, as stated by Meek. Compared with that shell, ours is much 
more elongated, and the beaks are placed proportionally nearer the front. 
Position and locality.—Carboniferous strata at Wild Band Pockets, 
Northern Arizona, 15 miles south of Pipe Spring. Collected by Mr. G. 
K. Gilbert, in whose honor the specific name is given. 
GASTEROPODA. 
Genus BELLEROPHON Montfort. 
BELLEROPHON SUBPAPILLOSUS White. 
Plate 34, fig. 3 a. 
Bellerophon subpapillosus White, 1879, Bull. U. S. Geol. Sur. Terr., vol. v, p. 218. 
Among the fossils here described, which Mr. Gilbert obtained from 
Wild Band Pockets, Northern Arizona, are some imperfect specimens of 
a Bellerophon which is closely related to B. uriti Fleming and B. carbo- 
narius Cox. In Powell’s Report on the Geology of the Uinta Mount- 
ains, p. 92, I gave a brief description of this form under the name of 
B. carbonarius var. subpapillosus ; the specimens then examined having 
been obtained from near the top of the Carboniferous series at several 
localities in Northwestern Colorado. In view of the constancy of the 
characteristics by which this form differs from the typical forms of B. 
carbonarius, | have decided to treat it as a distinct species, although I 
have no doubt of its genetic relation to B. carbonarius ; and it probably 
bears the same relation to B. writ also. 
Among the differences between this species and B. carbonarius is that 
the former is constantly of larger size than the latter as it is known 
throughout the Mississippi Valley and through the whole of its great 
vertical range in the Coal-measures there. The other characteristics 
which distinguish the two species from each other are also constant 
throughout their range and distribution respectively. The more con- 
spicuous of these characteristics as regards B. subpapillosus, aside from 
its greater size, consists in the studding of the surface of the outer part 
of the last volution, which is entirely plain in B. carbonarius, with 
slightly raised papille, arranged in rows corresponding to and contin- 
uous with the revolving strise which mark the remainder of the surface 
of both shells. 
B. subpapillosus is dharacheiste of the upper strata of the Carbonif- 
erous series in Northwestern Colorado and the adjacent region, and its 
presence among the collections made by Mr. Gilbert in Northern Ari- 
zona seems to indicate a similar horizon for the strata from which the 
latter were obtained. 
