32 HAWAIIAN AND OTHEE PACIFIC ECHINI. 



The tridentate pedicellaria^ have the valves very broad, thick, and 

 flat. They vary enormously in size, ranging from .50 to 5.5 mm. in 

 length ; the small ones liave the stalk about equal to the valves, but in 

 the large ones it is much less. The small ones are abundant everywhere; 

 the larger ones are on the interambulacra, while the largest are mainly 

 above the ambitus and often near the abactinal system. The largest are 

 20 to 30 in number, more or less, though they may be much fewer ; their 

 valves are always tapering and more or less distinctly pointed. 



Porocidaris variabilis A. Ag. and Clark. 



Plates 8, lG-22, and 23, figs. l-J,. 



An excellent series of specimens of this species was collected by the 

 "Albatross" from thirteen localities, in 202 to 34G fathoms, varying in size 

 from 77 mm. in diameter to 22 nnn. (Pis. 16-22; 23, figs. l-!i). In the 

 smaller specimens the primary radioles are much longer in proportion to 

 the diameter than in larger specimens. In the small specimen (Plate 

 22) of 22 mm. there are several of the primary radioles more tlian 76 nmi. 

 in length. In a specimen 35 mm. in diameter, the longest radioles are 

 122 mm. long (Pis. 20, 21). In a specimen -40 mm. in diameter (PI. 23, 

 figs. 1-Jf) the longest radioles are only 71 mm. long. In the largest 

 specimen examined (Pis. 10, 17) the longest radioles have a length of only 

 71 mm. The general appearance of the large primary radioles varies 

 greatly (PI. 8, figs. 12- iO) ; in the smaller specimens the majority are 

 pointed, the shaft is very delicately striated with minute serrations. The 

 shaft is a porcelain white, but towards the extremity it becomes yellowish- 

 brown, slightly fluted. The base of the spine above the milled ring is a 

 delicate salmon color. In older specimens there are but few white primary 

 radioles. The shaft of the radioles is of a light-brown color with only a 

 small part white ; the base of the spine is of a darker color. The shaft 

 of the radioles is also more deeply fluted, the serrations larger and more 

 blunt than in smaller specimens. The fluting becomes very marked and 

 quite deep towards the tip of the radioles, and many of the shorter and 

 stouter primary radioles spread somewhat at the tip (Pis. 16, 17; 23, figs. 

 1-Jf). The actinal primary radioles (PI. 8, figs. 10 and 20) are short, sligliLly 

 curved, deeply fluted, with large blunt serrations; the smaller radioles are 

 flattened; the lower part of the shaft of the larger radioles is porcelain 



