NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS — CLARK 



II 



Frequency at different depths Frequency at different temperatures 



t — A > i k « 



Degrees 

 Fathoms 1 2 Fahrenheit 1 2 



O-IOO 2 O 80-75 ° O 



I00-200 2 O 75-70 2 O 



20O-3OO 2 I 70-6s 2 



300-400 3 i 65-60 2 



400-500 3 1 60-55 2 



500-600 5 I 55-50 2 



600-700 5 1 50-45 2 



700-800 5 1 45-40 3 1 



800-900 3 1 40-35 5 1 



900-1000 3 1 35-30 1 



1000-1500 2 1 30-25 I o 



1500-2000 I I 



2000-3000 I I 



1 2 



Average depth 681 fathoms 936 fathoms 



Average temperature 49-8° Fahr. 40.0 Fahr. 



1. Basals separate. B it , ™ , 



^ Bathymetnc Thermal 



range range 



Pentacrinitidae (Atelecrinus; Pen- 



tacrinitida) 5-1350 36.0-71.0 



Apiocrinidae 565-940 36.7-38.1 



Phrynocrinidae 508-703 38.1-40.0 



Bourgueticrinidae (Monacho crinus, 



Demo crinus, Bythocrinus) 62-2217 37.4-40.5 



Plicatocrinidae (C 'alamo crinus, Hy- 



ocrinus, Gephyro crinus, Thalas- 



socrinus) 392-2575 31 -1-43-9 



2. Basals fused into a single calcareous element. 



Bathymetric Thermal 



range range 



Pentacrinitidae (except Atelecri- 

 nus and Pentacrinitida) 0-2900 28.7-80.0 



Bourgueticrinidae (Ilycrinus, Bathy- 



crinus, Rhizo crinus) 77-2535 30.9-48.7 



Plicatocrinidae (P til crinus) ...... 266-2485 35.3 



Primarily the basals form each a separate and distinct skeletal ele- 

 ment at the head of one of the interradial areas. 



But, if through reduction of the calyx in its relation to the visceral 

 mass, or in any other way, the basals lose their intimate connection 

 with the structures lying immediately within them, they also lose 

 more or less their individuality, becoming closely united and forming 

 a single skeletal element, a ring or " rosette," which in extreme cases 

 is functionally little more than a topmost columnal, for which, indeed, 

 it has often been mistaken. 



