94 The American Geologist. August. 1902. 
In addition to the feature of the primitive radianal, T. 
tiibcrculatits has a different general anal structure, that side 
being occupied by plates not in a vertical series, but resting 
on an angular posterior basal, more like that of Forhesio- 
criniis. It is obvious, therefore, that upon the above grounds 
it should be separated as a new genus, which I have done un- 
der the name Teuinocrinns. 
Frequent remarks have been made as to the difficulty of 
separating the genera of this group. It seems to me, how- 
ever, that they are about as well defined as in other groups. 
There are transition forms, it is true, but they are not more 
perplexing" here than elsewhere. I have found the following 
analytical arrangement, showing the mutual relations of the 
genera, to be reasonably convenient and satisfactory : — 
ANALYSIS OF THE GENERA. 
A. Arms contiguous ICHTHYOCRINIDAE. 
1. Radianal and anal .r. 
Arms isotomous ; no iBr Lccanocvinus. 
Pycnosaccus. 
Cyrtidocriniis. 
2. No radianal. 
Arms heterotomous Calpiocriiins. 
Arms isotomous 
. Anal x followed by 2 or more plates 
in succession. 
Radials separated by iBr all around Cleiocniiiis. 
Radials in contact except at anal side Clidochirus. 
Homalocriniis. 
Anal X alone, or with small triangular 
plate above Anisocrinns. 
Arms with dextrorse twist; no iBr Mcspilocriiiiis. 
Anal plates in tube-like vertical series, 
bordered by small, irregular plates ; 
iBr Pariclithyocriiius. 
No anals nor interbrachials Iclitliyocrinits. 
B. Arms divergent TAXOCRINIDAE. 
I. Anal side filled with well-defined plates 
not in vertical series. 
Radianal. 
Arms isotomous. 
Radianal in primitive position directly 
below r. post. R. ; iBr few Tcmnocrimis 
Radianal located obliquely under r. 
post. R. and between basals ; iBr 
numerous Sas.enocriniis. 
