46 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



2. Skeleton composed of less than a million ossicles. 



Batkymetric Thermal 



range range 



Pentacrinitidae (except part of 



Capillasterinse, Comasterinae, Zy- 



gometridae, Himerometridae, Ma- 



riametridse, Colobometridse, and 



Heliometrinae, and Pentacrini- 



tida) 0-2900 28.7-80.0 



Apiocrinidae 565-940 36.7-38.1 



Phrynocrinidae 508-703 38.1-40.0 



Bourgueticrinidse 62-2690 29.1-70.75 



Holopodidae 5-120 71.0 



Plicatocrinidse 266-2575 31. 1-43.9 



In the older crinoids the skeleton was usually composed of an 

 enormous number of ossicles. 



In the later and more specialized types the individual skeletal ele- 

 ments are as a rule very much less in number. 



This is a good example of specialization through suppression. 



Frequency at different depths 



Frequency at different temperatures 



Average depth 



Average temperature 



568 fathoms 

 52.5 ° Fahr. 



822 fathoms 

 49.5 ° Fahr. 



THE FAMILIES OF RECENT CRINOIDS, WITH THE CHARACTERS, 

 AS PREVIOUSLY GIVEN, PRESENTED BY EACH 



In the following pages each of the families including recent cri- 

 noids is given, together with the characters as just described which 

 it presents. 



