Boone, Echinodermata, Cruises of "Eagle" and "Ara," 1921-28 131 



Diadema setosum Th. Mortensen, Eehinoidea, D. Kgl. Dan. Vid. 

 Selsk. Skr., 7, Naturhg. og Math. Afd., I, p. 124, 1904; Eehinoi- 

 dea, Danish Ingolf Exped., vol. 4, pt. 2, p. 184, footnote, 1907. — 

 Verrill, A. E., Trans. Conn. Acad. Arts and Sci., vol. XII, 

 p. 323, pi. 34, fig. 1, text fig. 174, 1904-07. 



Centrechinus setosus Jackson, Mem. Boston Soc. Nat. Hist., vol. 7, 

 p. 28, 1912. — H. L. Clark, Papers Marine Biol. Carnegie Inst. 

 Washington, vol. X, p. 146, color plate 17, figs. 3 and 4, 1921. 



Diadema setosum H. L. Clark, Cat. Recent Sea Urchins, Brit. Mus., 

 p. 43, 1925. — Th. Mortensen, D. Kgl. Danske Vidensk. Selsk. 

 Skrifter Naturvidensk og Mathem. Afd. 9 Raekke, IV, 1, p. 17, 

 figs. 1-3, 1931. 



Suborder: Camarodonta. 



Family: ECHINIDAE. 



Genus : LYTECHINUS A. Agassiz. 

 Lytechinus variegatus (Leske). 



Plate 85. 



Type: Leske described the species in 1734, from material in the 

 Klein collection, now preserved at Erlangen; locality of type not 

 stated. 



Distribution : This is one of the common sea urchins of the tropical 

 west Atlantic, ranging from North Carolina and Bermuda, south- 

 ward through the Gulf of Mexico and West Indies, down to Rio de 

 Janeiro, Brazil. Littoral to 50 fms. 



Material examined: Eight beached tests from the West Indies, 

 Cat. no. 274. One specimen collected at Dry Tortugas, Florida, by 

 the "Ara," Cat. no. 273. 



Color: Very variable, ranging from rich violet to bright green or 

 creamy white. 



Habits: This species frequents sandy bottom and often disguises 

 itself by covering its test with seaweed and similar detritus. 



Life history: The life history of this species has been carefully 

 studied by Tennant, Journ. Exper. Zool., vol. 9, 1910 ; also by Morten- 

 sen, "Studies of the Development and Larval Forms of the Echino- 

 derms," p. 35, 1921, Copenhagen. 



Technical description : Agassiz 's description of this species, based 

 on a very extensive collection of specimens of varying ages and from 

 different localities, remains the standard diagnosis of L. variegatus. 



