504 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
length of the arms, rise only to a certain height, and are not closed from 
above. The plates, as a rule, are highly ornamented, strongly nodose, or 
extended into long spines. The dorsal cup is constructed of the same num- 
ber of plates, and arranged in exactly the same manner as in Lucalyptocrinus; 
generally, however, the basal concavity is wider, and 
only partly filled by the column. In the construction 
of the ventral disk also, the two genera have close 
affinities; the plates in both forms consist of four 
rings, and in both of them the first ring is composed 
of twenty plates, the second and third of four; but 
the fourth ring contains but four plates instead of ten, 
and these have no wing-like extensions at their outer 
faces; the upper parts of their arms are free, and rest 
directly against the walls of the anal tube. The parti- 
tion walls, of which there are twenty in this genus, 
are restricted to the plates of the first ring, and rise 
Callicrinus. 
Fic. 17. Side view 
of calyx, showing the rudi- 
mentary partitions. 
but little above their general height, never touching 
R=radials; J=costals; 77 = 
distichals; ir = interbrachi- 
als; id = interdistichals; irP 
= interradial partitions; idP 
= interdistichal partitions ; 
ipP = interpalmar partitions; 
i=the first or lower ring of 
plates in the tegmen, com- 
posed of ten large and ten 
the plates of the second ring. Five of the partitions 
are supported by the interbrachials, five by the inter- 
distichals; the remaining ten are interposed between 
the ten others, and rest upon the edges of two palmars. 
These latter partitions are formed by wing-like exten- 
sions from the ten smaller plates of the first ring; 
small subtrigonal pieces; 2 = 
the plates of the second ring, 
5 = those of the third ring, 
4 =the plates of the fourth 
ring. 
they rise to the same height as the others, and separate 
the two arms which in Lucalyptocrinus occupy the 
same compartment. The plates of the second and 
third rings either are flat, the general curvature excepted, or they show 
The 
four plates of the upper ring constitute the upper end of the anal tube, 
Arms robust throughout, 
some inclination to forming faces of attachment for partition walls. 
which generally has a quadrangular opening. 
closely folded, and composed, from the second or third plate up, of two 
The partitions by which they are separated 
Column 
rows of transverse pieces. 
rarely extend up higher than to one third the length of the arms. 
round ; the axial canal of medium size and pentangular. 
Distribution. — The greatest number of species occurs in the Upper Silu- 
rian of Gotland, and there are one or two at Dudley, England. The genus 
is represented in America by four species in the Niagara group. 
Callicrinus costatus (Hisinger) is the type of the genus. 
