248 HAWAIIAN AND OTHER PACIFIC ECHINI. 



and bare, carrying only 1-3 very small tubercles. They are usually all exsert 

 but in one specimen I is distinctly insert and in another it is nearly so. 



The interambulacral plates at the ambitus are rather more than twice as 

 wide as high. Each plate carries a small imperforate, non-crenulate, primary 

 tubercle and 6-8 well-spaced secondaries, some of which are nearly as large as 

 the primary. Miliary tubercles are small and abactinally they are few and very 

 indistinct; actinally they become more numerous and better defined. The 

 ambulacral plates are high, those at the ambitus half as high as wide and those 

 near the ocular plate as high as wide. Each plate carries a small primary tubercle 

 and 2-4 secondaries one of which is often nearly equal to the primary. The 

 pore-pairs are small, well spaced and form a nearly vertical series, especially 

 abactinally. The poriferous area is thus very narrow, occupying only the outer 

 third of each plate, though near the actinostome it becomes a little wider. At 

 the ambitus, the interambulacra are not quite twice as wide as the ambulacra. 



The buccal membrane (PI. 98, fig. 3) is heavily plated. The primordial 

 ambulacrals are approximated in pairs and are distinctly larger than the other 

 plates. All the plates are thick, white, and polygonal and carry more or less 

 numerous pedicellarise. In the small specimens, there are practically no gill- 

 cuts but in the large ones, the cuts are well defined though not very deep. 



The primary spines are remarkably short, slender, and pointed. They 

 show under the lens about a dozen longitudinal striations. The milled ring is 

 only imperfectly developed. The secondary spines are similar but much more 

 blunt. Miliaries are few and scattered, and are remarkably long and slender. 



Pedicellarise are abundant, the tridentate being the most common. The 

 globiferous pedicellarise are fairly common. The valves (PI. 93, fig. 4) are 

 slender, about .65 mm. long, with the base not quite half so wide. The stalks 

 are very slender, two or three times as long as the head, and there is no neck. 

 The heads contain numerous spicules which are distinctly bihamate and not 

 dumb-bell shaped; at least none of the latter were seen. The tridentate pedicel- 

 larise show great diversity in size, the valves (PI. 93, fig. 5) ranging in length 

 from .35 to 1.25 mm. The blade is moderately broad, rounded at the tip and 

 contains a small amount of calcareous mesh-work. In the small tridentates, 

 the valves are more compressed, there is no mesh-work, the margins are somewhat 

 more dentate and the tip is bent in more. The ophicephalous are not rare and 

 are rather conspicuous as the head is quite heavy and the stalks are long and 

 stout. The valves are somewhat constricted but not markedly so. They 

 measure about .40 mm. besides the loop which may be half as much again. The 



