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 less 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 almost 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 



large 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 deep and wide. The primary spines are short, rather stout, 



blunt, and not very conspicuous. 



The pedicellarise are fairly common but are not peculiar. The globiferous 

 have valves about .25 mm. long, the narrow tubular blade about as long as the 

 rather wide base, and terminating in a single long tooth. The ophicephalous 

 have valves of nearly the same length, with the loop adding about a third as 

 much more. The tridentate 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 triphyllous are very small, the valves measuring 



