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 

 form. 



CHIRODOTA DISCOLOR. Esch. 

 Chirodota discolor, Eschscholtz ; ZoOlogischer Atlas, PL X. f. 2. 



Hab. Sitka. 



CHIRODOTA VERRUCOSA. Esch. 

 Chirodota verrucosa, Eschscholtz ; ZoOlogischer Atlas, PL X. f. 3. 



Hab. Sitka. 



ECHINID^E. 



ECHINUS CHLOROCENTROTUS. 

 Echinus chlorocentrotus, Brandt ; I. 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 of 

 the very oblique rows, which are separated from each other 

 by rows of small tubercles. Interambulacral area with 



