ICHTHYOCRINIDAE 26l 



Family ICHTHYOCRINIDAE Angelin 



(Emend. Wachsmuth and Springer) 



Sagenocrinoidea with infrabasals horizontal, not appearing externally and tak- 

 ing NO PART IN THE CALYX WALL, SOMETIMES DISAPPEARING BY ATROPHY. CROWN ELON- 

 GATE OR ROTUND. Rays WIDENING FROM RADIALS UP, IN CLOSE CONTACT, USUALLY 

 INTERLOCKING OR ABUTTING THROUGHOUT OR ABOVE INTERBRACHIALS. 



Analysis of the Genera 



I. Rays in contact all around. 



Arms dichotomous, interlocking. IBr 2. 

 No anal or iBr. Post. B not differentiated. 



RA in form of R, under r. post. R Ichthyocrinus. 



No RA. 



Post. B not differentiated Metichthyocrinus. 



Post. B elongate Synaptocrinus. 



II. Rays in contact except at anal side. 



Arms dichotomous, interlocking. IBr 2. 

 RA in form of R, under r. post. R. 

 Anal x alone or followed by others. 



Post. B truncate. (IBB unstable, often appearing 



beyond the column) Clidochirus. 



Post. B not differentiated, and not touching anal x Cleistocrinus. 



III. Rays above radials partly or wholly separated. 

 RA not identifiable, or wanting. 



Arms dichotomous, usually abutting over iBr. 

 Anal x followed by others in single series. 



iBr few, usually in single series. IBr 3 Euryocrinus. 



iBr numerous, in" more than one series. IBr 2 Amphicrinus. 



Arms heterotomous. 

 iBr few or absent. 



Anal x followed by others in more than one series, 



suturally connected at sides Dactylocrinus. 



Anal x suturally connected at sides and with post. B 



followed by others in series, forming a tube Synerocrinus. 



No anal. Post. B not differentiated Wachsmuthicrinus. 



