304 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Test more or less depressed; anal plates of variable number and size, one or more dis- 

 tinctly larger than the others. 



Some of the buccal plates, usually 5, lack a tube-foot sagittiger. 



All of the buccal plates carry tube-feet. 



Genital pores near centre of genital plates. 



Buccal plates large, all 10 usually more or less in contact with each other, 

 though in some cases adjoining pairs may be well separated; area 

 within the buccal circle more or less plated. 

 Color yellow-orange or whitish; spines white, yellow-orange at base Forbesianus. 



Color red or reddish, the primaries lighter at tip ruber. 



Buccal plates small, more or less widely separated from each other; 

 area within their circle not well plated; color dull purplish red, 



often light sculptus. 



Genital pores at distal tips of genital plates. 



Buccal plates large, the two of each pair more or less in contact; area 

 within their circle more or less fully plated; genital plates little 



sculptured, if at all Agassizii. 



Buccal plates small, well separated; area within their circle with only a 

 few scattered plates; genital plates prettily sculptured depressus. 



Prionechinus Chuni D6d. 



Prionechinus Chuni Doderlein, 1906. Ech. Deuts. Tiefsee Exp. (" Valdivia" Ech.), p. 192. 



This seems to be the most sharply defined and easily recognized species in 

 the genus. There is nothing to add to Doderlein's very complete and satis- 

 factory discussion of the "Valdivia" material. 



The "Albatross" specimens, ranging from 2.5 to 11 mm. in diameter, were 

 taken at only a single place. 



Station 4126. Off Kahuku Point, Oahu, Hawaiian Islands. Bott. temp. 

 35.5. 743-1278 fathoms. Gy. s., for. 



Seven specimens. 



Prionechinus ruber A. Ag. and Cl. 



Prionechinus ruber A. Agassiz and Clark, 1907. Bull. M. C. Z., LI, p. 126. 



Plate 100, figs. 4-6. 



The larger of our specimens is 11 mm. in diameter while the smaller is only 

 7 mm. The former is 5.5 mm. high and has the abactinal system and actino- 

 stome, each 5 mm. across, while the smaller specimen is 3.5 mm. high and its 

 abactinal system and actinostome are each a trifle more than 3 mm. in diameter. 

 In the larger specimen, the primary spines are 5 mm. long, and there are 11 

 interambulacral and 12 ambulacral plates in each column; in the smaller speci- 



