526 Stimpson on the Crustacea and Echinodermata 
projecting and bifurcate below, notched above.  Respira- 
tory trees very slender; genital tubes two or three times 
divided. Color, yellowish-white, clouded with reddish 
above. Length of an alcoholic specimen four inches; 
thickness, two inches. 
Found at San Pedro, Cal., by Lieut. Trowbridge. 
The genus differs from Chirodota in the want of the cal- 
careous deposits of the skin so characteristic of the latter 
orm. 
CHIRODOTA DISCOLOR. Esch. 
Chirodota discolor, Escuscmorrz; Zodlogischer Atlas, Pl. X. f. 2. 
Hab. Sitka. 
CHIRODOTA VERRUCOSA. Esch. 
Chirodota verrucosa, Escuscnorrz ; Zodlogischer Atlas, Pl. X. f. 3. 
Hab. Sitka. 
ECHINIDA. 
ECHINUS CHLOROCENTROTUS. 
Echinus chlorocentrotus, BRANDT ; L. c. 64. 
This may be distinguished by its very short spines. 
Hab. Sitka, (Mertens.) Dr. Cooper informs me that a 
green Echinus is common on the shores of Puget Sound, 
which is probably this species. 
ECHINUS PURPURATUS.* Stimpson, n. s. 
Form depressed. Outline somewhat pentangular. Am 
bulacral areas of the same width as the interambulacrals : 
(sometimes even wider;) with eight pairs of pores in each o' 
the very oblique rows, which are separated from each other 
by rows of small tubercles. Interambulacral area W 
