48 PANAMIC DEEP SEA ECHINI. 



specimens of 16 mm. where the outline of the actinal system is decagonal 

 it remains about one half that of the test, as in a specimen of 5 mm. 



In a specimen 16 mm. in diameter (PI. 14, figs. GS) the height of the 

 coronal plates was 12 mm. and the apical system rose fully 4 mm. above 

 that. There were seven and eight primary interambulacral plates. 



In a specimen 13 mm. in diameter (Pis. 14, figs. 9-11', 18, figs. 3, 4.', 

 17, figs. 1, 2\ 20, fig. 3) the coronal plates rose to a height of 7.75 mm. 

 and the abactinal system 2.5 mm. above that. There were six and seven 

 primary tubercles differing from the older ones only in the smaller number of 

 miliaries surrounding tlie scrobicular area. The abactinal system measured 

 8 mm, in diameter, the anal system 3.25, and the actinal system 6 mm. 



©@(o)(o) 



8 mui. 10 III III. lo iiiiii. 10 mm. 



Fig. 79. Sai.ema mii.iap.is. 



In a specimen 10 mm. in diameter (PI. 18, figs, i, 2) the five and six 

 coronal plates rose to 8 mm. and the abactinal system was far less prominent 

 than in older specimens, rising only 1 mm. above that ; it measured 7 mm. 

 across (PI. 16, fig. 6), and was more circular, — the anal plates with dimin- 

 ishing size becoming proportionally larger as they decrease in number. 

 Compare PI. 16, figs. 2, Jf., G and PI. 17 figs. 2, 3. The actinal system 

 (PI. 16, fig. 10) of the same specimen measured 5.5 mm. in diameter. 



In a somewhat younger specimen, 8 mm. in diameter (Pis. 16, figs. 3, 4; 

 17, figs. G, 7 ; 20, fig. 2)^ the abactinal system measured 6 mm. acro-ss, the 

 anal system 2.2 mm. in diameter, the actinal system 4 mm. ; the height 

 7 mm. including the abactinal system ; there were six and .seven primary 

 tubercles. Fig. 83. In the youngest specimen collected, 5 mm. in diameter, 

 Fig. 82 (Pis. 16, figs. U 2\ 17, figs, ^j; 20, fig. 1), the test is much Hatter, 

 the height, including the abactinal system, is onh' 3 mm., the diameter of 

 the apical sj'stem 3.0 mm., of the anal system 1.5 mm., with only five large 

 ])rimary plates and the points of the smaller second set intercalated between 

 them ; the actinal system 2.2 mm. in diameter and the longest radiole 25 mm. 

 in length. 



Tlie anal system of Salcuia milians would seem to have started in the 

 youngest stage with five anal plates. They are still predominant in a 



