480 



THE AMERICAN NATURALIST [Vol. LII 



garious in habit, and the collector frequently finds a dozen 

 or more congregated beneath a half-buried stone or coral 

 mass.. A tiny pink species, Ophiothrix sp., with remark- 

 ably long arms, inhabits crevices in the coral. It is very 

 difficult to capture intact, because it, like most of the 

 <>plimn>ids, possesses to a remarkable degree the faculty 

 of self-mutilation. Many of the Hawaiian brittle-stars, 

 when disturbed or removed from the water, sever por- 

 tions of their arms piece by piece until finally nothing is 

 left but the central disc. This is capable of developing a 

 new set of arms ; and a detached arm can, under favorable 

 conditions, develop a new disc and a completed, series of 

 arms. The basket-stars, Cladiopluunc, have never been 

 collected on the Hawaiian reefs. 



The sea-urchins, Echinoidea, are richly represented, but 

 most of the species inhabit the deep offshore waters. 

 The inshore species are g 

 rocky situations along the < 



themselves. PodopJwra pedifera, for example, prefers 

 the black lava rocks and cliffs exposed to the full force of 

 the surf, and is so abundant that the zone of massive 

 basalt which it inhabits is literally honeycombed with its 

 burrows. Several species of Echinometra are also very 

 abundant ; these prefer the shallow waters of the lagoons. 



as along the outer edge of the 



in all 

 well as on the reefs 



>le-black specie-. f)i,„/, , 



' paucispinnm, 



Wit " ^•'"'''i'- awl-haped spmes. In the same situations 

 occurs Echhiothr'tx desori, a large form whose long spine? 

 are beautifully banded with gray and black. The curious 

 club-spined urchins, Heterocentrotes spp., occur here and 

 there along the reef, and are frequently exhibited in the 

 Honolulu Aquarium. The sea-biscuit, Brissus carinatus, 

 is a large, heart-shaped urchin, covered with short, brown 

 hair-like spines, and is occasionally found along the reef 

 - A number of the Hawaiian urchins are known to the 



iative> a> 



them for food. They may be purchased in the local 

 h markets. 



