

THE BENTHAL 217 



the gasteropods in the Indo-Pacific is governed by that of the coral 

 reefs, on which the molluscan fauna is especially varied. 78 Besides the 

 above-named Leptoconchus and Magilus, the family Coralliophilidae 

 is especially adapted to life in the reefs, the different forms belonging 

 to it having lost their radulae in adaptation to feeding on the coralline 

 slime, for which teeth are not needed. 



Some predaceous chaetopod worms which live concealed in the reefs 

 are characterized by a remarkable mode of reproduction. The palolo 

 worm, Eunice viridis (Fig. 45), of the South Seas may serve as ex- 

 ample. The eggs and sperm are developed only in the posterior division 

 of the worm, and these parts are cast off when mature, when they leave 



Fig. 46 Fig. 47 



Fig. 46. — Pistol crab, Alpheus bermudensis. About twice natural size. After 



Spence Bate. 

 Fig. 47. — Trapezia rujopunctata var. intermedia, natural size. After Miers. 



the reef and swarm out into the open surface water. This occurs twice 

 each year, at a predictable date, namely on the day before and the 

 day of the last quarter of the moon in October and November. 79 The 

 sea is then so filled with them that the natives gather them with 

 baskets for a feast. Eunice furcata has the same habit in the Dry 

 Tortugas. 80 



Crustaceans are exceedingly abundant in the reefs, variously con- 

 cealed in cracks and between the branches of the madrepores. The 

 alpheids, or pistol crabs, small, long-tailed decapods which make a 

 snapping sound with their claws (Fig. 46) , are closely correlated with 

 the corals in their distribution. Out of 79 long-tailed decapods taken 

 by Gardiner in the Maldive reefs, 76 were alpheids. Crabs are 

 abundant, especially the small Cyclometopa. The family Trapeziidae 

 (Fig. 47) is confined to coral reefs, where single species are restricted 

 to single reefs and occur only on single kinds of corals, as Trapezia 



