252 HAWAIIAN AND OTHER PACIFIC ECHINI. 



large, and broadly exsert, except I, which is insert or nearly so in specimens more 

 than 7 mm. h. d. Each ocular carries 1-3 small tubercles. The ocular pore is 

 well developed near the distal margin of the plate. 



The interambulacral plates are high, only those at the ambitus being nearly 

 twice as wide as high. Each plate carries a small, but well-developed primary 

 tubercle and 4-9 secondary tubercles, one or two of which approach the primary 

 in size. The ambulacral plates are remarkably high, as high as wide or higher. 

 Each plate carries a primary tubercle and 2-4 small secondaries of variable size. 

 The pores are relatively large, three pairs in each plate, and are placed close to 

 the interradial margin. The poriferous area is narrow and nearly straight. 

 The ambulacra are about three fourths as wide as the interambulacra at the 

 ambitus. 



The buccal membrane (PL 96, fig. 5) is very fully covered with thick white 

 plates, among which the primordial ambulacrals, although distinctly the largest, 

 are not conspicuous. The larger plates all carry pedicellarise in small numbers, 

 often only one to a plate. The gill-cuts are sharply defined but are not very deep. 



The primary spines are rather short, and though relatively thick at the base, 

 taper rapidly to a blunt point. They are finely, longitudinally striated. The 

 scattered secondaries are short, thick, and pointed. 



Pedicellarise are not at all common, though the ophicephalous, because of 

 their white color and long white stalks may be rather conspicuous. The globif- 

 erous pedicellarite are small and show no special peculiarities. The valves have 

 the usual tubular blade without lateral teeth and measure .25-.30 mm. in length. 

 The ophicephalous show considerable variation in size; the valves, which are 

 somewhat constricted above the base, range from .14 to .25 mm. in length, while 

 the articular loop adds .03-.07 more. The stalks are stout and long, exceeding 

 many of the secondary spines. No triclentate or triphyllous pedicellarise and 

 no sphseridia were observed. The calcareous spicules are distinctly bihamate. 



The color of the test is quite variable; actinally it is white like the plated 

 buccal membrane but abactinally it becomes pale brownish. The median 

 ambulacral and interambulacral areas abactinally are more or less brick-red or 

 less commonly reddish brown. There are traces of red also on the abactinal 

 system. In some specimens, there are patches of light green at the ambitus 

 and a similar color may sometimes be noted on the genital plates. The primary 

 tubercles, abactinally at least, are more or less reddish. The plates of the peri- 

 proct are white. The primary spines are pale red, lightest at the tip ; those on 

 the actinal side, especially in young specimens, show faint bands of red. 



