34 HAWAIIAN a:nd othek pacific echixi. 



iniliaries on the plates forming the angles of the pentagonal anal system. 

 The jH'oximal part of the madreporic genital is riddled ^vith pores. The 

 genital openings are large (a female PI. 18,. fig. l) and placed near the 

 distal edge of the genital plates. The actinal system (PI. 18, fig. 2) is pen- 

 tagonal, 25 mm. in diameter, with eight rows of ambulacral plates, and not 

 more than four or five small interambulacral plates. The latter are bare 

 or carry one indistinct miliary. The ambulacral plates carry minute secon- 

 daries on the actinal edge of the plates. 



In a specimen 36 mm. in diameter (PI. 23, figs. I-4) and 26 mm. in 

 height, there are six and seven interambulacral plates. The abactinal 

 system is circular, 16 mm. in diameter (PI. 23, fig. l); it differs only in size 

 from the structure of the abactinal system of the larger specimen described 

 (PI. 18, fig. /), and being that of a male it has small genital openings. 

 A comparison of the interambulacral plates of the specimens figured on 

 Plate 18 with those of PI. 23, figs 3^ 4, shows that the equatorial increase 

 of the test takes place more rapidly than the increase in width of the 

 median interambulacral zone covered by secondaries and miliaries. In 

 the smaller specimen there is only one circle of secondaries round the 

 scrobicular area, with a few irregularly arranged large miliaries filling the 

 angles of the interambulacral plates along the median line. The actinal 

 system is pentagonal (PI. 23, fig. ~) 14 mm. in diameter. There are but 

 five rows of ambulacral plates with three or four small elongated plates in 

 the small interambulacral space, four of the rows of ambulacral plates being 

 in contact along the interambulacral line, and leaving but a small angle for 

 the interambulacral actinal plates. 



In the specimen 22 nun. in diameter and 14 mm. in height, there are 

 six interambulacral plates. In the smallest specimen, 4.5 mm. in diameter 

 and ') nun. in height, there are already four and five interambulacral plates. 

 The louirest i)rimarv radiole is 14 mm. The secondaries are few in number 

 and aic niore or less cylindrical or club-shaped. The abactinal system 

 is very large, 2.5 mm. in diameter, and each genital plate carries a con- 

 spicuous perforate tubercle. The actinostome is less than 2 mm. in diameter 

 and is practically covered l)y the ten buccal plates, a pair in each am- 

 bulacrum. I'he pedicellariio are already conspicuous, and, like the primary 

 radioles, are strikingly similar to those of the ailult. In specimens of P. 

 Cobosi slightly lajgei", the structure of the abactinal system is ver}' similar 

 to that of this young individual. 



