NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS CLARK 



2. Calyx forming a platform upon which the viscera rest, more 

 or less supported by the arm bases. 



Bathymetric Thermal 



range range 



Pentacrinitidse 0-2900 28.7-80.0 



Apiocrinidse 565-940 36.7-38.1 



Phrynocrinidas 508-703 38.1-40.0 



Bourgueticrinidae 62-2690 29.1-70.75 



In the majority of the older crinoids, as well as in the pentacrinoid 

 young of the comatulids, the visceral mass is protected dorsally and 

 laterally by two or three alternating ring's of plates, with the summit 

 of the column covering the opening in the center of the innermost 

 ring. 



In the later types, as in the developing young of the comatulids, 

 we see a progressive decrease in the relative size of the calyx plates, 

 as a result of which they become more and more restricted to the 

 dorsal apex, leaving more and more of the lateral portion of the 

 visceral mass exposed, until finally they become so reduced as to 

 serve merely as a platform upon which the dorsal apex of the visceral 

 mass rests, the lateral portions being supported by the arm bases. 



The reduction of the crinoid calyx from the primitive condition of 

 a cup entirely enclosing and protecting laterally and dorsally the vis- 

 ceral mass, is obviously specialization by inhibition and progressive 

 suppression of the skeleton forming power ; it is correlated with a 

 similar reduction affecting other portions of the skeleton. 



Frequency at different depths Frequency at different temperatures 



, « > r— *- ■ 



Degrees 

 Fathoms 1 2 Fahrenheit 1 2 



O-IOO I 2 80-75 O I 



100-200 I 2 75-70 I 2 



2OO-3OO I 2 70-65 O 2 



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



4OO-50O I 2 60-55 2 



5OO-60O I 4 55-50 O 2 



60O-70O I 4 50-45 O 2 



700-800 I 4 45-40 I 2 



800-900 I 3 40-35 I 4 



900-1000 I 3 35-30 1 2 



1000-1500 1 2 30-25 o 2 



1500-2000 1 2 



2000-3000 1 2 



1 2 



Average depth .' 808 fathoms 785 fathoms 



Average temperature -f? 1 " ! \ Fahr. 50.1° Fahr. 



137-5°J 



