250 HAWAIIAN AND OTHER PACIFIC ECHINI. 



is largest, covering half of the area or more. The genital plates are approxi- 

 mately equal and broadly in contact with each other. Each carries one second- 

 ary tubercle on the proximal margin, and occasionally there is a miliary tubercle 

 beside it. The madreporic genital is perforated by only a few pores and these 

 are situated in an elevation near the centre of the plate. The oculars are very 

 small, all broadly exsert; each one carries a small secondary tubercle or two. 

 There are no genital pores visible but with a lens, the ocular pores can be seen 

 close to the distal margin of the plates. 



The interambulacral plates at the ambitus are rather high, but the greater 

 part of the surface is covered by the big primary tubercle, around which a few 

 minute secondary tubercles are scattered. The ambulacral plates are high but 

 their primary tubercles are very unequally developed. On some plates they are 

 very large occupying most of the surface, while on others they are so small as to 

 be more naturally called secondaries. There are usually more primaries de- 

 veloped on one side of the area, than on the other, giving the ambulacra a one- 

 sided appearance. The pore-pairs are very small, three for each plate, and the 

 poriferous area is a narrow, nearly straight, vertical line. At the ambitus, the 

 ambulacra are about three fourths as wide as the interambulacra. 



The buccal membrane (PI. 96, fig. 2) is thin and although well covered with 

 plates, it is not heavily plated as in euerces. The primordial ambulacral plates 

 are much larger than the others and form a nearly closed ring. There seem to be 

 no spines or pedicellarise borne by any of the actinostomal plates. Gill-cuts are 

 scarcely to be detected at all. 



The primary spines are noticeably long and correspondingly conspicuous, but 

 are rather slender and taper to a point. Those at the ambitus are the longest 

 and those of the ambulacra are smaller than the interambulacral. The secondary 

 spines are very few; they are long and slender. 



Pedicellarise appear to be very scarce. The globiferous valves (Plate 93, 

 fig. 10) have the blade tubular and terminating in a single tooth, without lateral 

 teeth. They are relatively large, measuring about .45 mm. in length. The 

 ophicephalous do not show any special peculiarities but the valves are constricted 

 above the base. No tridentate or triphyllous pedicellarise were found, neither 

 were there any sphgeridia, or spicules in the tube-feet. No doubt the poverty 

 of the available material accounts in large part for this lack. 



The ground color of this species is white but abactinally there is, under a lens, 

 a more or less evident yellow-green shade. This color is most marked on the 

 outer ends of the genital plates, on the periproctal plates, along the sides of the 



