CALYPTOCRINID#. 341 
zontally, except their extreme lower ends, which take part in the basal 
concavity. Costals, first distichals and first interbrachials curving rapidly 
upwards, so that the sides near the top of the cup are parallel with corre- 
sponding parts of the opposite side. Surface of plates, as shown from the 
gutta percha impressions, beautifully ornamented with elongate nodes or 
ridges passing out from the centres of the plates to their sides, but not con- 
tinued to adjoining plates. 
Basal concavity narrow, and moderately deep. The radials rapidly 
tapering to their lower ends and rather small, not larger than the second 
costals, which are considerably larger than the first. First costals quad- 
rangular, once and a half as wide as long; the second hexagonal, being 
truncated at the upper end. First distichals about a third smaller than the 
upper costals; the second quite small and the palmars still smaller. First 
interbrachial larger than the radials, almost as wide as high, those of the 
second row together smaller than the first; the interdistichal sub-rhomboidal, 
the upper and lower angles truncated. 
Horizon and Locality. — Niagara group; Racine, Wisc., and Chicago, Ills. 
Ltemarks. —The basal concavity in the casts is deeper than it appears 
in the gutta percha impressions, and there are shallow grooves passing out 
from it in a radial direction, which are not seen upon the impressions, and 
give to the cavity in that state of preservation a decidedly pentapetalous 
aspect. In specimens in which the plates are but partly dissolved, the sur- 
faces generally show concentrating lines around the margins of the plates, 
which probably represent mere lines of growth. 
Eucalyptocrinus ventricosus W. and Sp. (nov. spec.). 
Plate LXXXII. Figs. 11 and 12. 
Syn. Zucalyptocrinus celatus, Rommer, 1860 (not Hall 1843); Silur. Fauna West. Tenn , 
p. 48, Plate 4, Figs. 3 a-e. 
A small species, in its general form subovate, slightly depressed at the 
poles, its greatest width a little above the arm bases. Dorsal cup low 
saucer-shaped, the sides evenly rounded, its height less than half the length 
of the arm compartments; the plates flat or nearly so, marked in well pre- 
served specimens by irregular, delicate lines running to the sides, but not 
communicating with those of adjacent plates, 
Basal concavity narrow and very deep, obscurely pentangular at the 
