42 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



to consider it as an indication of specialization through suppression 

 of all of the functions of pinnules, which has permitted a radical 

 change in their structure. 



Frequency at different depths 



Frequency at different temperatures 



Pentacrinitidae (part of Capillaste- 

 rinae, Colobometridae, Zenometri- 

 nse, Pentametrocrinidse and Atele- 

 crinidae, and all of the Perometri- 



nse) 0-1050 



Phrynocrinidae 508-703 



Bourgueticrinidae 62-2690 



Plicatocrinidae 266-2575 



2. All of the proximal pinnules present. 



Bathymetric 

 range 



Pentacrinitidas (except part of Ca- 

 pillasterinae, Colobometridae, Ze- 

 nometrinae, Pentametrocrinidse, 

 and Atelecrinidae, and the Pero- 



metrinae) 0-2900 



Apiocrinidae 565-940 



Holopodidae 5-120 



37.0-80.0 

 38.1-40.0 

 29.1-70.75 

 3I-I-43-9 



Thermal 

 range 



28.7-80.O 

 36.7-38.I 

 71.0 



In the earlier crinoids all of the pinnules were commonly present, 

 but with the decrease in the size of the visceral mass and the corre- 

 sponding increase in the size and in the length of the arms which we 

 are, in a general way, able to trace from the earlier to the later types, 



