346 HAWAIIAN AND OTHER PACIFIC ECHINI. 



actinal membrane fully plated. The latter character, taken with the small size, 

 was misleading and the possibility of their being young Pseudoboletias did 

 not suggest itself. But the presence of deep actinal cuts for the gills, spines 

 on the buccal plates, and four pairs of pores in each arc, show their true 

 position beyond doubt. The buccal plates are large and near together but are 

 not as nearly in contact as in large specimens. One of the specimens is badly 

 distorted, ambulacrum II being malformed, sunken, and without pores above 

 the ambitus. The arrangement of the ocular plates in the other specimens is 

 interesting as showing that the adult character is not acquired very early in all 

 cases. In the two largest specimens, ocular I is broadly insert while ocular V 

 is still exsert, although very nearly in. In the two smallest specimens ocular I 

 is broadly insert while V is narrowly so. It seems fair to assume that in this 

 species ocular I becomes insert before the individual is 10 mm. h. d. while ocular 

 V comes in during the growth in diameter from 10 to 20 or perhaps 25 mm. 



The coloration of these specimens is very plain. The test is whitish with a 

 more or less pronounced green tinge when cleaned. The plated actinostome 

 is almost pure white. The spines vary from white to deep pink, in four of the 

 specimens being distinctly pink. 



The pedicellarise are remarkably numerous and varied, no less than six 

 different forms being found on a single specimen. The globiferous occur in two 

 different forms, a larger (PI. 92, fig. 12) without glands on the stalk and with 

 valves (PI. 92, fig. 15) .65-.8S mm. long, and a smaller, with glands on the stalks 

 (PI. 92, 13) and valves only about .20 mm. in length. The ophicephalous pedi- 

 cellarise are common everywhere but are not peculiar; the valves measure .20- 

 .40 mm. in length besides the "loop" which may be half as much again. The 

 tridentaie occur in two very different forms, one (PI. 92, fig. 14) with very slender 

 valves, about .70 mm. long; the other, with broad valves (PI. 92, fig. 17) .50- 

 .90 mm. long. The latter are common everywhere but the former are rare and 

 seem to occur only abactinally. The triphyllous are very small, with valves 

 only .12-. 14 mm. in length. There are 4 or 5 sphseridia (PI. 92, fig. 18) on the 

 lower part of each ambulacrum. Calcareous spicules occur in both the pedicels 

 and the heads of the globiferous pedicellariae. The latter are smaller but are 

 not otherwise different. The spicules are usually C- or (- shaped but they may 

 have an irregular branch or two; they are sometimes perfectly bihamate. As 

 Mortensen makes the form of these spicules one of the chief subfamily characters 

 in his classification, it seems desirable to call attention to their variability. 



The "Albatross" took no adult specimens of Pseudoboletia but the young 

 ones were taken at the following stations : 



