i6 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



It may be remarked that in certain fossil types there are analogous 

 cases of doubling of the radials through a transformation into radials 

 of plates originally of quite different significance. 



Frequency at different depths 



Frequency at different temperatures 



Average depth 



Average temperature 



i. Interbrachials present. 



Bathymetric 

 range 



Pentacrinitidas (Comasterinae, Calo- 

 metridse, Mastigometra, Ante- 

 don, Erythrometra, Pentacrini- 

 tida) 0-1350 



Plicatocrinidae 266-2575 



2. Interbrachials absent. 



Bathymetric 

 range 



Pentacrinitidae (except Comasteri- 

 nx, Calometridas, Mastigometra, 

 Antcdon, Erythrometra, Penta- 



crinitida) 0-2900 



Apiocrinidae 565-940 



Phrynocrinid« 508-703 



Bourgueticrinidse 62-2690 



Holopodidae 5-120 



666 fathoms 

 35-8° Fahr. 



822 fathoms 

 49.5 ° Fahr. 



Thermal 

 range 



36.O-80.O 



3 1. 1-43.9 



Thermal 

 range 



28.7-80.0 



26.7-38.I 



38.I-4O.O 



29.I-70.75 



7I.O 



Interbrachials, characteristic of most fossil crinoids, occur, usually 

 as small and thin, more or less irregular and poorly developed, plates, 

 in many recent types. 



Usually, however, they are quite absent, at least in adults. 



