HETEROCENTROTUS. 377 



Lanai, H. I. 



Hilo, Hawaii, H. I. 



Puako Bay, Hawaii, H. I. 



One hundred and twenty-eight specimens. 



Podophora pedifera Agass. and Des. 



Echinus pedifer de Blainville, 1825. Diet. Sci. Nat., XXXVII, p. 97. 

 Podophora pedifera Agassiz and Desor, 1846. Ann. Sci. Nat., (3), VI, p. 374. 



This species has been confused with the preceding but the large series collected 

 by the "Albatross" in the Paumotus shows clearl}^ that it is quite distinct and 

 that its specific characters are well marked and constant. They need not be 

 discussed here however as they are fully dealt with in the monograph on the 

 genus, already referred to. 



The specimens brought home by the "Albatross" were collected on the 

 reefs of 



Rangiroa, Paumotu Islands. 



Fakarava, Paumotu Islands. 



One hundred and eleven specimens. 



COLOBOCENTROTUS. 



Brandt, 1835. Prodrom. desc. Anim., p. 266 (or 66). 

 Type-species, Colobocentrotus Mertensii Brandt, 1835, 1. c. 



It is a curious fact that so far as any reliable records show this genus is con- 

 fined to the Bonin Islands, and few specimens have found their way into collec- 

 tions. There is some doubt as to whether all the known specimens should be 

 referred to a single species {Mertensii Brandt) or not, but there seems to be a 

 second {Stimpsoni A. Ag.). 



The two are distinguished as follows : — 



Short diameter of test more than .90 of long diameter so that ambitus is nearly circular . . Mertensii. 

 Short diameter of test less than .90 of long diameter so that ambitus is elliptical . . Stimpsoni. 



Heterocenthotus. 



Brandt, 1835. Prodrom. desc. Anim., p. 265 (or 65). 

 Type-species, Echinus mammillatus Lmn6, 1758. Syst. Nat., ed. 10, p. 667. 



There seems to be general agreement that this well-known genus contains 

 two, and only two, species, and an examination of all the available material 



