628 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Family HIPPOLYTID^E. 



HIPPOLYTE, SP. 



On one of the harbor buoys at La Hougue. near Cherbourg, Malard found 

 Antedon bifida in immense numbers, literally covering the chain. There were 

 three distinct color types (1) violet-red, more or less deep; (2) orange yellow, 

 inclining toward saturn red; and (3) alternate white and red with whitish pinnules. 



The Plippolyte occurring with them were of the same colors. 



Family PONTONIID^E. 



Although the first known species of this family, described as far back as 1829, 

 is a commensal in bivalves, and many of those subsequently established are com- 

 mensal on sea urchins, starfishes, ascidians, corals, sponges, and especially in 

 lamellibranchs, it was not until 1902 that any were known to be commensal on 

 comatulids. 



In that year Mr. L. A. Borradaile, who hald accompanied Prof. J. Stanley 

 Gardiner during his explorations in the Maldive and Laccadive archipelagoes, 

 published an account of cases of commensalism between these prawns and reef -living 

 crinoids. 



In 1915 Borradaile described these species, and with them others which had 

 been collected by Lieut. F. A. Potts at Torres Strait; and in the same year Potts 

 published his own notes upon the latter. 



An excellent monographic account of the whole family was published by 

 Borradaile in 1917. 



Like most of the commmensals living on the comatulids, these prawns subsist 

 on the minute organisms crowded together in the currents of water flowing down 

 the ambulacral grooves toward the mouth. 



Borradaile states that in this family the color varies greatly, the animals being 

 striped, spotted, or suffused in very different ways and with very different colors, 

 while the differences between species are often as great between species of the same 

 genus as between those of different genera. In the cases at present known the 

 colors are usually gaudy and conspicuous when the prawns are removed from their 

 proper environment, though in some instances, at least, their coloration harmonizes 

 very strikingly with that of the natural surroundings. 



Nothing is known of the color changes which doubtless occur during life, or 

 in regard to the way in which there arises a correspondence between the coloration 

 of the individual and that of its surroundings, or as to the value this may have 

 to the prawn. 



The species of this family known to be commensal on comatulids are the 

 following : 



PERICUMENES ( PERTCLIMENES ) COMMENSALIS BORRADAILE. 



This species was described from specimens collected by Lieutenant Potts at 

 Torres Strait and found on Comanthus annulatus. 



