232 BOPYRiDii:. 



ISOPODA . BOP YRIDJE. 



NORMALIA. 



Genus— PHRYXUS, Rathke. 

 [Phryxus and Pleurocrypta, Hesse.) 



This genus was instituted by Rathke, for the reception 

 of a species of the Bopyrid(2, parasitic on a prawn of the 

 genus Hippolyte, remarkable for the very swollen and 

 unsymmetrical form of the female, of which the legs on 

 one side are nearly abortive in the full-grown state, 

 but more especially for the large size of the lobes or 

 plate-like branchial appendages of the tail, by which it 

 at once differs from the two preceding genera. 



The whole of the species hitherto discovered, including 

 three new ones now first made known to the public, are 

 parasites on various crustaceous animals belonging to the 

 Anomourous and Macrourous divisions, including not 

 only the more typical Hippolyte, but also the aberrant 

 genera Pagurus and Galathea. 



The male in the species which served for the establish- 

 ment of the genus is very minute and elongated in form, 

 with the head transversely ovate, with two minute dark 

 points indicating the eyes ; the upper antennae are very 

 minute, and consist of three joints of equal length, but 

 gradually becoming more slender to the tip, which is 

 furnished with a number of hairs ; the lower antennae are 

 much longer, and consist of eight joints, also gradually 

 attenuated to the tip. The mouth is transformed into a 

 small conical protuberance rising from a semicircular 

 space. The pereion is composed of seven segments 

 of nearly equal size, each with the sides rounded and 

 wide apart (in specimens distended from having been 



