NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS CLARK 



IO - 



Frequency at different depths 



Fathoms 

 O-IOO 



I 00-2OO 



200-300 



3OO-4OO 



4OO-50O 



5OO-60O 



600-700 



70O-80O 



80O-9OO 



900-1000 

 IOOO-I500 

 I50O-200O 

 2OOO-3OOO 



Average depth 



Average temperature 



Frequency at different temperatures 



Degrees 



Fahrenheit 



80-75 

 75-70 

 70-65 

 65-60 



6o-55 

 55-50 

 50-45 

 45-40 

 40-35 

 35-30 

 30-25 



828 fathoms 

 45.8° Fahr. 



2 

 

 1 

 o 

 o 

 o 

 o 

 o 

 

 

 o 

 o 



60 fathoms 

 7 i.o° Fahr. 



I. Column composed of short cylindrical ossicles bearing radial 

 crenellae on their articular faces. «.,♦,,„„,.♦,.;,. Thermal 



range 



3 1. 1-43-9 



Bathymetric 

 range 



Plicatocrinidae 266-2575 



2. Column not composed of short cylindrical ossicles bearing radial 

 crenellae on their articular faces. Bathymetric Thermal 



range range 



( Pentacrinitidae) 0-2900 28.7-80.0 



Apiocrinidce : 565-940 36.7-38.1 



Phrynocrinidse 508-703 38.1-40.0 



Bourgueticrinidae . ... . 62-2690 29.1-70.75 



Holopodidse 5-120 71.0 



In all primitive types, and in practically all of the Palaeozoic cri- 

 noids, the column is composed of a great number of short cylindrical 

 ossicles with their circular articular faces marked with radial crenellae. 



But in most of the families of the Articulata, and in a few of the 

 earlier forms, such for instance as the Platycrinidae, the column, in 

 addition to a marked decrease in the number of the columnals, has 

 been greatly reduced in volume through the reduction in size of 

 each of the component ossicles which, instead of being circular in 

 cross section, have become elliptical, the long axes of the ellipses 

 representing the diameter of the original circle, and the difference 

 in length between the two axes indicating the amount of calcareous 

 matter lost ; rigidity is maintained in this (the so-called " bourgueti- 



