44 HAWAIIAN AND OTHER PACIFIC ECHINI. 



test of the Laganidae is usually very flat and it is never highly arched although 

 it is occasionally moderately thick and concave beneath. The primary spines 

 are not peculiar, but are solid, slender, and pointed, while the secondaries are 

 characteristic, as already described (p. 14). All three kinds of pedicellariae 

 are present but are not usually distinctive. 



Although reported from Zanzibar, Madagascar, and the Persian Gulf, 

 the family is characteristic of the East Indies and Southeastern Japan. It is 

 not represented in the Atlantic or Eastern Pacific Oceans. The grouping of the 

 species in genera has been a source of no little difference of opinion among 

 students of the family, owing to a belief that the number of genital pores is 

 variable, some individuals having four and some five, even in the same species. 

 After examining hundreds of specimens of at least twelve species, I feel satisfied 

 that the number of genital pores is a very constant character and serves very well 

 to distinguish two genera within the family. 



Key to the Genera of Laganidae. 



Genital pores 5 or 6, present in all interambulacra Laganum. 



Genital pores 4, wanting in posterior interambulacrum Peronella. 



Laganum. 



Gray, 1825. Ann. Phil., 26. p. 427. {Lagana by error). 

 Type, Echinodiscus laganum Leake, 177S. Add. ad Klein, p. 140. 



In de Meijere's very careful and admirable revision of this genus Siboga 

 Ech., p. 113-131), no attempt is made to group the species in subgenera or to 

 separate a genus Peronella, though there is a brief discussion of some of the 

 points involved. In his key, de Meijere uses the position of the genital pores 

 as a primary mark of distinction, between the species; while I do not question 

 its importance, I am inclined to think the number is a more fundamental char- 

 acter. He further points out important characters in the position, form and 

 covering of the periproct, to which earlier writers had paid small heed. Hi- 

 interesting discoveries in regard to the spines have already been discus 

 (p. 14). Of his four new species, I think two must be referred to the very vari- 

 able L. fudsiyama, although further study on Still more abundant material 

 may show that I am quite wrong. For the present. I recognise six spec* 

 Laganum. 



