22 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



2. Column without a terminal stem plate. 



Bathymetric Thermal 



range range 



Bourgueticrinidse 62-2690 29.1-70.75 



The columns of the earlier crinoids typically (thought by no means 

 always) terminated in an expanded base composed of a number of 

 enlarged columnals which, in later types, became simplified as a 

 single terminal stem plate from which the column more or less 

 abruptly arises. 



The presence of a terminal stem plate appears to be of fundamental 

 significance, and therefore any type without it must be considered 

 as possessing a highly specialized type of column. 



The absence of a terminal stem plate indicates specialization 

 through suppression of a fundamentally important skeletal structure. 



Frequency at different depths Frequency at different temperatures 



, * \ r ^ 



Degrees 

 Fathoms 1 2 Fahrenheit 1 2 



O-IOO 2 I 80-75 I O 



I0O-20O 2 I 75-70 2 I 



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



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



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



50O-60O 4 I 55-50 I I 



600-700 4 1 50-45 1 1 



700-800 4 I 45-40 2 1 



800-900 3 1 40-35 4 1 



900-1000 3 1 35-30 2 1 



1000-1500 2 1 30-25 1 1 



1500-2000 2 1 



2000-3000 2 1 



1 2 



Average depth 785 fathoms 808 fathoms 



Average temperature 5 2 -0° Fahr. 44.8° Fahr. 



1. Radicular cirri present. Bathymetric Thermal 



range range 



Bourgueticrinidas 62-2690 29.1-70.75 



2. Radicular cirri absent. Bathymetric Thermal 



range range 



(Pentacrinitidse) 0-2900 28.7-80.0 



Apiocrinidae 565-940 36.7-38.1 



Phrynocrinidse 508-703 38.1-40.0 



Holopodidce 5-120 71.0 



Plicatocrinidse 266-2575 31. 1-43.9 



