34 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



Frequency at different depths Frequency at different temperatures 

 a ^ * N 



Degrees 

 Fathoms 1 2 Fahrenheit 1 2 



0-100 i 3 80-75 O I 



IOO-200 I 3 75-70 I 3 



2O0-30O 2 2 70-65 I 2 



3OO-40O 2 2 65-60 I 2 



400-50O 2 2 60-55 I 2 



500-600 3 3 55-50 1 2 



600-700 3 3 50-45 1 2 



700-800 2 3 45-40 2 2 



800-900 1 3 40-35 3 3 



900-1000 1 3 35-30 1 2 



1000-1500 1 2 30-25 o 2 



1500-2000 1 2 



2000-3000 • 1 2 



1 a 



Average depth 700 fathoms 756 fathoms 



Average temperature 49-1° Fahr. 51.6 Fahr. 



1. A suture (or pseudo-syzygy) between the ossicles of the IBr 



SeneS - Bathymetric Thermal 



range range 



Pentacrinitidse (Comatula, Co mas- 

 ter, Zygometridse, Pentacrinitida) 0-1350 36.0-80.0 



Phrynocrinidse 508-703 38.1-40.0 



Plicatocrinidae 266-2575 31. 1-43.9 



2. A ligamentous articulation (or synarthry) between the ossicles 

 of the IBr series. „ ,, T , , 



Bathymetric thermal 



range range 



Pentacrinitidse (except Comatula, 



Comaster, Zygometridae, Penta- 

 crinitida) 0-2900 28.7-80.0 



Apiocrinidse 565-940 36.7-38.1 



Bourgueticrinidae 62-2690 29.1-70.75 



Holopodidse 5-120 71.0 



So far as can be ascertained, the union between the plates of the 

 IBr series in the earlier crinoids was by means of a more or less 

 featureless suture. 



This suture in the later types became developed into a very dis- 

 tinctive ligamentous articulation known as the synarthry,. composed 

 of two lateral ligament bundles separated by a strong dorso ventral 

 ridge running entirely across the apposed articular faces. 



The development of a union composed of large and definite liga- 

 ment bundles from a union of scattered and diffuse fibers occupying 

 a much greater surface indicates a great reduction in the skeleton 



