ACTINOCRINID AL (ROEMER). 
(Emended and restricted by W. and Sp.). 
Monocyciic. THE LOWER BRACHIALS WITH WELL DEFINED INTERBRACHIALS BETWEEN | 
THEM, FORMING AN IMPORTANT PART OF THE DORSAL CUP. RADIALS IN CONTACT 
EXCEPT AT THE POSTERIOR SIDE, WHERE THEY ARE SEPARATED BY A HEXAGONAL 
ANAL PLATE, WHICH IS FOLLOWED BY TWO INTERBRACHIALS WITHOUT A SECOND 
ANAL. “BASALS FORMING A HEXAGON. 
Analysis of the Genera. 
Basals 3, equal. Arms biserial, branching alternately from the main divisions of the rays. 
A. ANUS AT THE END OF A TUBE. 
1. ILnterbrachials connected with the interambulacrals. 
a. Calyx lobed, interradial spaces depressed. 
Anal tube long, central. The branching in the calyx 
above the distichals at alternate sides from every 
second or third plate. Bifurcations of the free arms, 
if any, at long intervals . . Ap ays cee See 
Rays produced into arm-like tubular extensions, rising to 
the full height of the crown, giving off arms from 
AUUSTITERTE HS MCS, SEs We cS oar ee oma a ee 
Anal tube short, excentric. Ventral disk largely pre- 
dominating over the dorsal cup. Rays widely sepa- 
rated. Arms heavy, generally bifurcating in the free 
state, the branches divergent. . .. . 
2. Interbrachials not connected with the interambulacrals. 
a. Calyx not lobed, arms about equidistant, given off in a more 
or less continuous ring around the calyx ; anal tube long, 
central. Bifurcations beyond the costals from every brachial 
an the calyx ; arms simple. 
Arms directed upward. Ventral disk conical, gradually 
PAS CHMS MIM TOMbNC MGM C N= Megtbee rade cele eee Sas tape 
Arms very numerous, their lower portions directed out- 
ward, incorporated into the calyx, and forming a broad, 
© slencleinares (oor naiwOuls. valid“ aa ae) Baan ha Oe, 
B. ANUS WITHOUT A TUBE. 
a, All bifurcations in the calyx given off from the first brachial 
of successive orders. 
Interbrachials connected with the interambulacrals ; in- 
terspaces between the rays and their subdivisions 
channeled; arms arranged in groups; ventral disk 
Ine mmisMeTiC ANUS EXCOUbRICHM vi slo. yl s+ es 
-— 
4 
EL 
Actinocrinus. 
Steganocrinus. 3 
Amphoracrinus. 
Cactocrinus. 
Teleiocrinus. | 
/ 
Physetocrinus. 
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