A NEW FOSSIL CRINOID GENUS—KIRK 153 
RHOPOCRINUS PROBOSCIDIALIS (Worthen), new combination 
Poteriocrinus proboscidialis WorTHEN, in Worthen and Meek, 1875, p. 518, pl. 
31, fig. 1. “Upper division of St. Louis limestone, Carondelet, Missouri.” 
(Ste. Genevieve?.) 
Poteriocrinus (Scaphiocrinus) proboscidialis WACHSMUTH and SprincEr, 1880, 
p. 114 (339). 
In addition there are at least two new species in the collections. 
Geologic and geographic distribution—The genus as known is 
chiefly found in the Chester. One species, Rhopocrinus probosei- 
dialis (Worthen), was described as from the upper part of the St. 
Louis. This might well be Ste. Genevieve as now known. Another 
undescribed species is from the “Ste. Genevieve” near Huntsville, 
Ala. Another undescribed species is from the Gasper of the same 
region. ‘Troost’s species R. municipalis, judged by the lithology of 
the matrix, may well be Gasper. The type species, R. spinosus, is 
from beds stated to be Glen Dean. 
Relationships—Rhopocrinus has no apparent relationship with 
any known upper Mississippian crinoid genus. Among lower Mis- 
sissippian genera it most nearly resembles Pachylocrinus. Rhopo- 
crinus Ynay readily be distinguished from Pachylocrinus by its 
turbinate cup and parendotomous arms as against the depressed, 
bowl-shaped cup and endotomous arms of the latter. 
RHOPOCRINUS SPINOSUS, new species 
PLATE 16 
Of this species there are three well-preserved crowns, one with 
some 14 cm. of column attached. In addition, there is a partial set 
of arms, more complete in the distal portion than in any of the 
crowns. The crowns, though of fairly large size for Chester inadu- 
nates, appear to be of medium size for the species. The crown is 
compact. With the relatively inconspicuous cup and the many 
branched arms with their spinous axillaries the crinoid presents a 
striking appearance. 
The dorsal cup is low and turbinate. It is composed of thick 
tumid plates. There is a sharply defined groovelike depression 
between each pair of radials. The 7BB& are small, not visible in 
lateral view, and almost completely covered by the column. The 
basals are relatively small. ‘The radials are large. The radial facet 
is linear and extends almost the full width of the radial. FA is large, 
resting on post and r post BB, but not entering deeply between them. 
A is likewise large and rises well above the plane of the RR. AT 
is likewise large. 
There are two /Br in each ray. The /Br are low and heavy. In 
the r post & of one of the paratypes the first bifurcation seems to 
