NO. 10 PHYLOGENETIC STUDY OF RECENT CRIN01DS CLARK 



59 



In this connection the Pentacrinitidse deserve more detailed exami- 

 nation. Very many characters are represented in this exceedingly 

 large and very heterogeneous group by both components of the 

 contrasted pairs, one of which is found in a — usually large — major- 

 ity, while the other occurs in a — usually small — minority of the 

 genera. 



In the preceding lists the totals represent all of the characters 

 under each heading ; hence many characters in this family are given 

 in the totals for both (i) and (2) ; such characters are neutral so 

 far as their effect upon the general total is concerned. 



If we eliminate this neutralization of one of the components of a 

 pair by the other by considering only the components of each pair 

 which are either represented alone or in the majority of the genera 

 our results will naturally be somewhat different. 



This method will give us the average state of specialization to 

 which the family has attained, through eliminating the influence of 

 a few conservative types which by the other method are accorded far 

 more than their true phylogenetic importance. 



THE TRUE PHYLOGENETIC SEQUENCE OF THE CRINOID 

 FAMILIES HAVING RECENT REPRESENTATIVES 



Judged on the basis of the preceding tables, the proper phyloge- 

 netic sequence of the crinoid families including recent species is as 

 follows : 



Pentacrinitid^e .... 28 (1) 



Holopodidse 15 (1) 



Bourgueticrinidse . . 18 (1) 



Apiocrinidse 17(1) 



Phrynocrinidse .... 20 (1) 

 Plicatocrinidse .... 30 (1) 



[10(1)] 



34(2) 

 18(2) 

 17 (2) 

 16(2) 

 14(2) 

 9(2) 



[26 (2) ] difference 



6(2) [16 (2)1 

 3(2) 

 1(1) 

 1(1) 

 6(1) 

 21 (1) 



128 (1) [no (1)] 108 (2) [100 (2)] difference 20 (1) [10 (1)] 



