DERMATODIADEMA HORRIDUxM. 



65 



covered by irregularly shaped minute calcareous platcH varying in out line; 

 from circular to very narrow elongate plates. 



In a specimen of 18 nnn. in diameter with nine primary inlcrambulacral 

 plates, Fig. 97, the height was 11.5 mm. and the apical system 18.5 mm. 

 It differed mainly in size from the specimen just described. The anal 

 system, however, had larger plates round the anal opening, eight in 

 number, and somewhat comma-shaped ; the larger anal plates are covered 

 with small miharies. In a specimen of 19 nmi. in diameter there were 



18 mm. 



Fig. 97. D. horridum. 



10.5 mm. 



Fig. 98. D. horridum. 



seven and eight primary tubercles, as in the larger and the smaller specimen 

 alluded to above. The longest radioles of specimens of 19 to 20 mm. in 

 diameter, taken on the third or fourth largest interambulacral plates, 

 measured about 40 mm. in length ; they are very brittle and delicate .'.nd 

 rarely found unbroken at the tip. 



In a specimen of 14 mm. in diameter (PI. 24, figs. 10-12) the longest 

 radiole was 26 mm., the apical system 8.2 mm. in diameter, the anal 

 system 6.1 mm., the height of the test 10 mm., the greatest width of 

 the ambulacral system 2.2 mm., the diameter of the actinal system 5.1 mm., 

 and the number of primary interambulacral tubercles six and seven. In 

 this stage of growth there are but two miliaries to each ambulacral plate. 

 Along the median interambulacral line the miliarias are placed in the 



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