A. 



H. 



GlarJc- 



-Groups of Recent Crinoids. 



71 



Himerometridge 





33 fathoms 



Capillasterinae 



189 



fathoms 



Colobometridse 





45 



ee 



Atelecrinidae 



308 



ee 



Mariametridse 





45 



ee 



Thysanometrinse 



338 



ee 



Ptilometrinse 





54 



ee 



Zenometrinae 



383 



ee 



Zygometridaa 





76 



ee 



Charitometridae 



464 



ee 



Comasteilnae , 





90 



ee 



Thalassometrinae 



50V 



ee 



Perometrinse 





133 



ee 



Heliometrinae 



633 



cc 



Calometridse 





142 



ee 



Plicatocrinidae 



952 



ee 



Antedoninae 





146 



ee 



Pentametrocrinidse 



1193 



ee 



Comasterinae 





ISO 



ee 



Bourgueticrinidae 



1415 



ee 





Bathymetrinae 



1801 fathoms 







Average 



for all the famil 



ies 435 fathoms 





In the preceding table the families Stephanometridse, Tropio- 

 metridse and Holopodidse, monotypic, and Apioerinidse, and 

 Phrynocrinidae, insufficiently known, are omitted. 



The average ranges of the contrasting groups are as follows : 



More specialized 

 Articulata 412 fathoms 



Pentacrinitidae 529 " 



Comatulida 429 " 



Oligophreata 167 " 



and of the stalked groups : 



Less specialized 

 Inadunata 952 fathoms 



Bourgueticrinidse 1415 " 

 Pentacrinitida 629 " 



Macrophreata 691 " 



Pentacrinitidas 



529 fathoms 



Pentacrinitida 



629 " 



Bourgueticrinidse 



Holopodidse 



Plicatocrinidse 



1415 " 

 115 " 



952 " 



The average bathymetric range of the families of cri- 

 noids existing in the recent seas varies between 33 fathoms in 

 the Himeroinetridse and 1801 fathoms in the Bathymetrinse 

 (tig. 1, upper border of the black areas). In examining the 

 list of contrasted groups it is clearly evident that the more 

 specialized the group the less becomes its average bathymetric 

 range. The same thing is indicated in the list of the stalked 

 types, if we bear in mind that the family Holopodidse is 

 restricted to the Caribbean Sea and therefore does not come 

 into competition with the more widely spread forms, and that 

 the genera of the Plicatocrinidse are not sufficiently known to 

 enable us to make any definite statements in regard to it. 



In the following list the families of crinoids which include 

 living species are given, arranged according to the average 

 depth of habitat (fig. 2, upper border of the black areas) : 



