120 bulletin: museum of comparative zoology. 



Valdivia Echini, p. 121), 1ms suggested, ophicephalous pediccllariae probably 

 occur in most if not all of the genera proposed by Mortensen. Those of tenue 

 are very similar to those figured by D derlein for Sperosoma durum. — The color 

 of the "Albatross" specimens is violet above, becoming deep reddish-purple 

 actinally, while the " Challenger " specimens were " yellowish-gray," but in the 

 general appearance and the arrangement of the tubercles there seem to be no 

 important differences between the two series. 



Station 4928. In Colnett Strait, Japan, 1008 fathoms. 

 " 5084. Off Omai Saki Light, Japan, 918 fathoms. 



Four specimens. 



Sperosoma quincuneiale de Mem. 

 Sperosoma quincuneiale de Meijere, 1904. Ech. Siboga-Exp., p. 40, PL 13, figs. 

 166-176. 



A number of Echinothurids, closely resembling P. tenue, prove on careful ex- 

 amination to be Sperosomas, which we are unable to distinguish from quincuneiale, 

 though none of the specimens is as large as de Meijere's type. They range from 

 45 mm. to 170 mm. in diameter and are all more or less deep violet in color. The 

 actinal primary spines are provided with large and conspicuous white " hoofs." 

 The arrangement of the ambulacral pores abactinally is very characteristic. 

 Station 4957. Between Kagoshima and Kobe, Japan, 437 fathoms. 

 5079. Off Omai Saki, Japan, 475-505 fathoms. 

 " 5080. Off Omai Saki, Japan, 505 fathoms. 

 Eight specimens. 



Sperosoma biseriatum Dod. 



Sperosoma biseriatum Dbderlein, 1901. Zool. Anz., 23, p. 20. 



We refer to this species, but not without some hesitation, a badly mutilated 

 specimen of Sperosoma, easily distinguished from the preceding by the arrange- 

 ment of the ambulacral pores abactinally, which are just as Doderlein (1906, 

 p. 152; PI. 19, fig. 1) describes and figures them for biseriatum. The color 

 and the pedicellariae show slight differences, however, for the test of this speci- 

 men was obviously deep purple, and the valves of the pedicellariae have a straight, 

 smooth margin. It is quite possible that this specimen really represents an un- 

 described species. 



Station 4766. Between Atka Island and Bowers Bank, Bering Sea, 1766 

 fathoms. 



One specimen. 



Sperosoma giganteum A. Ag. and Clark. 



This remarkable Echinothurid measures nearly 320 mm. in its greatest horizon- 

 tal diameter. The color is very deep purple, almost black when in shadow. The 

 ambulacra are extraordinarily wide, for on the abactinal surface just above the 

 ambitus they measure over 100 mm. while the interambulacra are little over 70. 

 The outer and inner columns in each half of each ambulacrum are made up of re- 



