278 HAWAIIAN AND OTHER PACIFIC ECHINI. 



The test is well arched with a circular, or in the largest specimen somewhat 

 pentagonal ambitus. It is very completely covered with tubercles, but in the 

 type and in the large specimen, a sunken zigzag line is more or lass marked in the 

 abactinal part of both the ambulacral and interambulacral areas. Seen from 

 above, the small specimen and the type show distinctly, twenty radiating series 

 of primary tubercles, two series in each area; these are of approximately equal 

 size and are decidedly larger than the numerous accompanying secondaries. 

 In the large specimen these twenty series are much less conspicuous as some of 

 the secondaries particularly at and near the ambitus are almo.st as large as the 

 primaries. Each ambulacral plate at the ambitus carries a primary tubercle, a 

 large secondary near the inner end of the plate and three to five small secondaries. 

 Each interambulacral plate has a large secondary tubercle on each side of the 

 median primary and there are four to six small secondaries also. Scattered 

 miliary tubercles occur in both areas. The abactinal system (PI. 97, fig. 6) is 

 noticeably small and the periproct is covered by few plates. The madreporic 

 genital is decidedly swollen and larger than the others; in the largest specimen 

 it has a single tubercle on the proximal margin but in the other specimens it has 

 none. Each of the other genitals carries two to four large tubercles. The 

 oculars are rather small, each with a large tubercle. In the type they are all 

 exsert, though I is only slightly so, and V is more nearly insert than any of the 

 other three. The same condition is found in the small specimen, but in the 

 largo one, I is broadly insert and V is only barely excluded. The poriferous 

 areas are broad, the rather large pores being arranged in quite oblique arcs of 

 three pairs; at the peristome the areas are narrower and the arcs are more nearly 

 vertical. The actinostome (PI. 97, fig. 5) is large, twice the diameter of the 

 abactinal system. The buccal membrane is thin and perfectly bare, except 

 for the small primordial ambulacrals. The gill-cuts are very well marked and 

 are moderately dooii and wide. The primary spines are short, rather stout, 

 blunt, and not very conspicuous. 



The pe(lic(»llariir are fairly common but are not peculiar. The glohi'fcrous 

 have valves about .2") nun. long, the narrow tul)ular blade about as long as the 

 rather wide l)ase, and terminating in a singl^^ long tooth. The ophkfphalous 

 have valves of nearly the same lengtli. with tlie loop adding about a third as 

 nnich more. The Indcntntc are chiefly actinal in position and have valves, 

 half a millimeter long, more or less; these valves are somewhat curved, com- 

 pressed at the base of the blade and somewhat expanded distally, where they are 

 in contact with each other. The triphylloiif! arc very small, the valves measuring 



