350 HAWAIIAN AND OTHER PACIFIC ECHINI. 



gill-cuts and more or less heavily plated buccal membrane (PI. 98, fig. 5) are 

 equally important and diagnostic. The short, small spines and the character- 

 istic globiferous pedicellaria? are notable additional features. The genus appears 

 to be monotypic and is probably confined to the Australian region. The records 

 from Mauritius and New Zealand are open to very grave doubt. 



Heliocidaris. 



Agassiz and Desor, 1846. Ann. Sci. Nat., (3), VI, p. 371. 



Type-species, Echinus omalostoma Valenciennes, 1846, Voy. "V6nu3." Zoophjtes, PI. 6, fig. 2. 



= Echinus tuberculatus Lamarck, 1816, Anim. s. Vert., Ill, p. 50. 



The reasons for considering tuberculatus the type of this genus have already 

 been given fully (p. 281) and need not be repeated here. .As thus understood 

 Heliocidaris is a fairly homogeneous group of five species confined to the Pacific 

 Ocean, three of the species being characteristic of the Australian region. A fourth 

 species, stenopora (new name for mexicana A. Ag.) is very httle known; the 

 specimens upon which it is based are supposed to have come from Lower Cali- 

 fornia; the species it.self is well characterized but that its home is really in the 

 eastern Pacific needs verification. It cannot continue to bear its original name, 

 mexicana, for it is entirely distinct from the Heliocidaris jnexicana of Louis 

 Agassiz and Desor described many years earlier. It may be called stenopora, 

 because of the narrow al)actinal poriferous areas. The fifth species, crassi- 

 spina (A. Ag.) is Japanese and resembles Strongylocentrotus nudus (A. Ag.) 

 quite closely, but can always be distinguished by the number of pore-pairs in 

 an arc. It api)cars that crassispina is quite distinct from E. tuberculatus Lamk., 

 and that Authocidaris homalosto?na Liitken, and Toxocidaris purpurea von Mart. 

 arc .synonyms of crassispina. It also includes Toxocidaris globulosa \. Ag., as 

 d(>l(M-miiie(l from examination of one of the type-specimens in the U. S. National 

 Alu.soum, kindly loaned through Mr. Austin 11. Clark. Of the three Australian 

 species of Ilrlincidaris, enjthrogrnnnna (Val.) and tubcrculata (Lamk.) are quite 

 distinct but it would not bo surprising t<^ have it demonstrated that armi^era 

 {\. .\g.) is simply a form of erylhrogratnnm. Witiiout intermediate specimens, 

 the two arc retained for the i)resent. The five species of Heliocidaris may be 

 distinguislied ivs follows: — 



Pore-pairH 7 or S in (\'H'l> arc, r.ar(>ly 0. 



I'rinijiry spino-s short (20 mm. db ) and very stout (2 or 3 mm. in diameter) armigera. 



Primary .spin<\s longer and much more slender. 



