314 CLARK: CORRELATION OF PHYLOGENETIC SPECIALIZATION 



The averages given in the preceding table are plotted in 

 figure 1. 



In this we see that the more speciahzed characters outnumber 

 the more primitive down to 250 fathoms, but from that point 

 downward the more primitive characters outnumber the more 

 speciahzed. 



Unfortunately the course of the lines in figure 1 is so irregular 

 as to render difficult a true appreciation of the interrelationships 



0-&0 

 50-100 

 100- IbO 

 150-i:00 

 200-:<:50 

 250-300 

 300-550 

 350-400 

 400-450 

 450-500 

 500-!f0 

 550-600 

 600-650 

 650-700 

 700-750 

 750-800 



aoo-eeo 



650-900 

 900-950 

 950-1000 

 1000- U 00 

 1100-1^00 

 lEOQ-1300 

 1300-1400 

 1400-1500 

 1500-1600 

 1600-1700 



1700-ieoo 



ieoo-1900 



19 00 -2000 

 2000-2500 

 2500-3000 



25 3;: 



36 40 



44_ 46 



Fig. 1. The bathymetrical distribution of structural characters in the recent 

 crinoids; , the more primitive characters, including those under the head- 

 ing "General;" — . — , the more primitive characters, without those under the 



heading "General;" , the more specialized characters, including those 



under the heading "General;" , the more specialized characters, with- 

 out those under the heading "General." 



of the two sets of characters. This difficulty may best be over- 

 come by ascertaining the excess of the primitive or of the spe- 

 cialized characters at the various depths. The figures repre- 

 senting this are given in the following table. 



Plotting these (fig. 2), we find that above 250 fathoms the 

 specialized characters predominate; if we include the characters 

 under the heading "General" we find a well marked node at 50- 



