? 
130 GEOLOGICAL SURVEY OF THE TERRITORIES. ’ 
especially with the Burlington division of that series, it differs too much 
specifically from any described form of that genus to need detailed com- 
parisons. 
Position and locality —Upper Coalmeasures, “30 miles west of Hum- 
boldt, Kans.” The type of this species is among the collections of the 
National Museum, but the record of the name of the collector has been 
destroyed by accident. 
Genus ARCH AOCIDARIS McCoy. 
ARCH ZOCIDARIS CRATIS White. 
Plate 33, fig. 2 a. 
Archeocidaris cratis White, 1876, Powell’s Rep. Geol. Uinta Mts., p. 109. 
Compare Archocidaris mucronatus Meek & Worthen, Ilinois Geol. Survey, vol. ii, p. 
295, pl. 23, fig. 3 ; 
Among the collections brought by Proféssor Powell from the middle 
division of the great Carboniferous series at the confluence of Grand 
and Green Rivers, Utah, is a single spine only of this species. The col- 
lections of the geological survey of Nebraska, in the cabinet of the 
Smithsonian Institution, also contain another spine. These are all that 
are known of the remains of this species, but as they are so character- 
istic, and so different from those of any described species, it is thought 
best to base a specific description upon them. 
Spines slender, gradually tapering from base to point; shaft orna- 
mented with sharp, distant spinules, each about one and a half milli- 
meters long, and pointing strongly upward; basal ring prominent, plain, 
except the fine crenulation of its edge, and situated very near the prox- 
imal end of the spine. Surface apparently smooth. 
Length, about 60 millimeters; diameter jrst above the basal ring, 
about 4 millimeters. 
This species is certainly very closely related to uM mucronatus Meek 
& Worthen (loc. cit.) from the Chester limestone of the Subcarboniferous 
series of Illinois, as shown by the enly parts of the animal yet discov- 
ered; so closely indeed that we should hardly feel warranted in referring 
our examples to any other than that species if they had been found as- 
sociated, or even in formations that are geologically equivalent. It 
is true that there exist between considerable portions of the faunz of 
the Chester limestone and the Upper Coalmeasures, respectively, very 
close relationships. Furthermore, certain of the brachiopoda found in 
the first-named formation are not specifically distinguishable from cer- 
tain species found in the last-named one. The difference, however, in 
the Echinodermic faunz of the two formations is quite marked, the 
species here described presenting a closer relationship with a Chester 
limestone form than does any other known Echinoderm. Not only is 
there a marked difference between the Echinodermic fauna of the Ches- 
ter limestone and that of the Upper Coalmeasures, but there is almost 
as great a difference between the Echinoderms of the different members 
of the Subcarboniferous series. In other words, the vertical range of 
fossil species of Echinoderms is perhaps more restricted than that of any 
other class of fossils. It is certainly much more limited than that of 
the Brachiopoda. 
With these facts in view, it is thought best to give a new specific name 
to the fossil here described, although it is so similar in general character 
with A. mucronatus. Compared with that species, the spines of this one 
are more slender, more directly tapering from base to point; the basal 
ring is a little more prominent, and the spinules less numerous. 
