NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS CLARK 



25 



III. DISK 



1. Disk entirely covered with plates. 



Bathymetric Thermal 



range range 



Pentacrinitidse ( Zygometridae, Calo- 



metridae, Pentacrinitida) 0-1350 36.0-80.0 



? Apiocrinidae 565-940 36.7-38.1 



Holopodidae 5-120 71.0 



Plicatocrinidae 266-2575 31. 1-43.9 



2. Disk naked, or with scattered granules. 



Bathymetric Thermal 



range range 



Pentacrinitida? (Comatulida, except 



Zygometridae and Calometridae) . 0-2900 28.7-80.0 



Phrynocrinidae . .508-703 38.1-40.0 



Bourgueticrinidae 62-2690 . 29.1-70.75 



In the earlier crinoids belonging - to the order Camerata, as in the 

 very young of the comatulids, the disk is always entirely covered 

 with plates, which form a solid pavement over it. 



Only in the later types, chiefly in the Articulata, does this disk 

 armament become less and less complete, eventually disappearing 

 altogether. 



The partially plated or unplated disks of many of the later crinoids 

 furnish an example of specialization through suppression of a 

 fundamental primitive character. 



Frequency at different depths Frequency at different temperatures 



t ' * ' 1 — i 



Degrees 

 Fathoms 1 2 Fahrenheit 1 2 



O-IOO 2 2 80-75 I I 



IOO-200 2 2 75-70 2 2 



20O-300 2 2 70-65 I 2 



3OO-4OO 2 2 65-60 I 2 



400-500 2 2 60-55 I 2 



500-600 3 3 55-50 1 2 



600-700 3 3 50-45 1 2 



700-800 3 3 45-40 2 2 



800-900 3 2 40-35 3 3 



900-1000 3 2 35-30 1 2 



1000-1500 2 2 30-25 2 



I5O0-20OO I 2 



2OOO-30O0 I 2 



1 2 



Average depth • 707 fathoms 791 fathoms 



Average temperature 52.8° Fahr. 50.7 Fahr. 



