NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS CLARK 



Frequency at different depths 



Fathoms 



O-IOO 



100-200 



200-300 



3OO-4OO 



4OO-50O 



50O-60O 



60O-70O 



7OO-80O 



80O-9OO 



goO-IOOO 



1000-1500 



I5OO-2O0O 



20OO-3OOO 



Frequency at different temperatures 



I * ^ 



Degrees 

 Fahrenheit 



80-75 



75-70 



70-65 

 65-60 



60-55 

 55-50 

 50-45 

 45-40 

 40-35 

 35-30 

 30-25 



Average depth 



Average temperature . 



i. Basals present. 



777 fathoms 

 48.8 Fahr. 



771 fathoms 

 50.2 Fahr. 



Bathymetric 

 range 



Pentacrinitidas (Atelecrinidse; Pen- 



tacrinitida) 5-1350 



Apiocrinidse 565-940 



Phrynocrinidce 508-703 



Bourgueticrinidae 62-2690 



Plicatocrinidaa 266-2575 



2. No basals. 



Bathymetric 

 range 



Pentacrinitidas (Comatulida, ex- 

 cept Atelecrinidas) 0-2900 



Holopodida? 5-120 



Thermal 

 range 



36.O-71.O 

 36.7-38.I 

 38.I-4O.O 

 29.I-70.75 



3 1. 1-43.9 



Thermal 

 range 



28.7-80.O 

 71.0 



In the crinoids, including the developing" comatulids, the two sets 

 of plates which appear to be of the greatest importance are the 

 basals and the radials, the former true calyx plates (corresponding 

 to the echinoid genitals) and the latter properly speaking arm plates, 

 though always forming part of the calyx cup. 



It is only in types of very late occurrence, and, among the coma- 

 tulids, very late in the ontogeny, that the basals become atrophied and 

 disappear. 



The elimination of the basals from the calyx in the more perfected 

 types indicates phylogenetic advance through suppression of one 

 of the most fundamental crinoid structures. 



