NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS CLARK 



* 6 « 2 r, - 



J? £ w £ n c -2 



U U Q < Ph O H 



Holopodidae I 2 3 1 2 1 10 



Pentacrinitidae 2 1 1 4 1 2 11 



Apiocrinidae :... 4 3 o 3 2 1 13 



Bourgueticrinidae 3 4 2 2 3 1 15 



Phrynocrinidae 5 4 2 5 2 1 19 



Plicatocrinidae 6 5 4 6 3 1 25 



If, however, we consider the Pentacrinitidae on the basis of the 

 average specialization, that is, if we consider each of the pairs of 

 characters of which it exhibits both components on the basis of the 

 majority representation alone, disregarding the small minority repre- 

 sentation, this family easily takes precedence over the Holopodidae. 



EXAMINATION OF EACH OF THE STRUCTURAL UNITS IN 



DETAIL 



A critical study of each structural unit, on the basis of the con- 

 trasted characters as previously given, is of considerable interest. 



In the following tables each of these units is listed separately, the 

 families in each case being arranged according to their relative 

 specialization in regard to the unit under consideration, with the 

 most specialized at the head of the list. 



When the total is the same in two families, the one which possesses 

 the higher number of specialized characters (or the lesser number 

 of generalized characters) is given precedence. Families with 

 identical totals are bracketed. 



Calyx 



1. Holopodidae 2 (1) 



2. Pentacrinitidae 8 (1) 



3. Bourgueticrinidae 5 (1) 



4. Apiocrinidae 4 (1) 



5. Phrynocrinidae 5 (1) 



6. Plicatocrinidae 6 (1) 



S (2) difference 3 (2) 



30 (1) 



35 (2) difference 5 (2) 



Column 



1. Pentacrinitidae 1 (1) 



2. Holopodidae 3 (1) 



3. Apiocrinidae 5 (1) 



f Phrynocrinidae 4 (1) 



^Bourgueticrinidae 4 (1) 



5. Plicatocrinidae 6 (1) 



23 (1) 



19 (2) difference 4 (1) 



