126 Bulletin, Vcmderbilt Marine Museum, Vol. IV 



References: Cidaris affinis A. Piiilippi, Arch. f. Naturgh., I, p. 351, 

 * 1845. — M. Sars, Middelhavets Littoral Fauna, p. 110, in Zool. 



"^acts, XV; original publication in Nyt Mag. f. Naturvidensk, 



r..i IX and X, 1857-59.— Wyville-Thompson, Proc. Royal Soc. 



Londcb, vol. XX, p. 492, 1872; Ann. Mag. Nat. Hist., 1872, 



vol. 10, ser. IV, p. 302. — Mortensen, Danish Ingolf Exped. 



Echinodea, vol. IV, pt. 1, p. 35, pi. 1, fig. 1, pi. 6, figs. 9-10, 



pi. 8, fig. 2, pi. 9, figs. 1, 8-9, 11-12, 17-19, 21-24, pi. 11, figs. 1, 22, 



1903. 

 Cidaris stokesi L. Agassiz and DeSor, Ann. Sci. Nat. Ill, ser. I, 



vol. VI, p. 326, 1846-47. 

 Dorocidaris papillata (Leske), A. Agassiz, Rev. Ech., p. 254, (in 



part), pi. 1, fig. 5, 1872.— H. L. Clark, Bull. U. S. Fish. Comm, 



vol. XX, part 2, p. 252, 1901. 

 ^tyJocidaris affinis Mortensen, Echinod. Deutsch. Sudpolar Exp., 



p. 52, 1909.— H. L. Clark, Iowa Studies Nat. Hist., vol. IX, 



p. 105, 1920-21. 



Genus: EUCIDARIS Gray. 

 Eucidaris thouarsii (Valentin). 



Plates 80 and 81. 



Type: The type series of this species was collected in California 

 and the Galapagos Islands, and is deposited in the Paris Museum. 



Distribution : From Lower California to Panama and the Gala- 

 pagos Islands. Littoral. 



Material examined : Three large specimens, Hood Island, Gala- 

 pagos Islands, March, 1928, Cat, no. 228. Three young specimens 

 from "Webb Cove, Albemarle Island, Galapagos Islands, February 3, 

 1928, Cat, no. 229, collected by the "Ara." 



Color : Unrecorded. 



Life history: The larval stages of this urchin have been studied 

 and figured in part by Dr. Mortensen. 



Technical description : The ' ' pencil urchin ' ' of the tropical 

 American Pacific coast is superficially very similar to its West Indian 

 congener, E. tribuloides, but is readily distinguished therefrom by the 

 fact that thouarsii has the median area of the interambulacra wider 

 but more closely granulated and in having the primary spines much 

 stouter, relatively shorter and with distinctly coarser sculpturing. 



