90 HAWAIIAN AND OTHER PACIFIC ECHINI. 



will not be out of place. There are no constant dififerences between the 

 pedicellarige of Dermatodiadema and those of Aspidodiadema, but there are 

 such differences between the larger pedicellarise of some of the species 

 of Dermatodiadema which are useful in their identification. 



The size and form of the pedicellarice show an extraordinary diversity, 

 as many as seven different kinds sometimes occurring on a single specimen, 

 while most individuals have at least four. There can generally be found 

 triphyllous, ophicephalous, and tridentate pedicellariae ; in some individuals, 

 two forms of triphyllous occur, while there are very commonly two forms 

 of tridentate present, and there may be three or four. The stalks of the 

 ])odicellari8e are calcareous rods, more or less enlarged, and fenestrated at 

 the ends, the extent of the fenestration depending chiefly on the size of the 

 pedicellaria. 



The tridentate pedicellariae in their most common form have the valves 

 long and slender (PI. 50, figs. 7, 1^), usually straight, but sometimes curved ; 

 tiiese may be called the " slender irideniate." Other very large pedicellaria) 

 are usually present of which the three valves are very broad and deep in 

 proportion to their length and have the blade more or less filled by a 

 calcareous network (PI. 50, figs. 1, 6, 11). These pedicellariae are called 

 *' globifere " by Doderlein, which is convenient but inaccurate, as they are 

 certainly not homologous with the globiferous pedicellarice of the other 

 Diadematoida. Mortensen calls them " large ophicephalous," and while in 

 some cases their resemblance to ophicephalous pedicellarise is apparent, the 

 absence of an " articular loop " and their great size are objections to regard- 

 ing them as such. As de Meijere calls them " grosse tridentate," and we 

 incline to the view that that name best expresses their real character, we 

 shall d(\si";nate them as " stout tridentate.'' Althouijjh these stout triden- 

 late pedicellaria) usually have the blade rather deep, with the sides converg- 

 ing to a blunt point, they sometimes occur with broad, rather flat blades 

 and wide tips (PI. 50, fig. 3) ; such pedicellaria? may be designated as *• form i." 

 Another peculiar form is rarely found, which is quite intermediate be- 

 tween the tridentate and ophicephalous pedicellarii\}, having the " articu- 

 lar loop " of the latter and the blade free from a calcareous network, but 

 with the general appearance of the former (PI. 50, fig. 4); these may be 

 called " form r." 



The slender tridentate pedicellaria? are very common, and occur on all parts 

 of the test, even on the abactinal system and the buccal membrane. The 



