No. 6. — Reports on the Scientific Results of the Expedition to 

 the Eastern Tropical Pacific^ in charge of Alexander Agassiz, 

 hy the U. S. Fish Commission Steamer " Albatross " from 

 October, 1904-, fo March, 1905, Lieut. Commandek L. M. 

 Garrett, U. S. N., Commanding. 



II. 



Description of a new germs of Isopods, typical of a peculiar family. 



By Harriet Richardson. 



In the recent voyage, 1904-05, of the Steamer "Albatross" to the 

 Eastern Pacific a very peculiar Isopod was collected, which does not seem 

 to belong to any of the known families of the order. Although it was 

 found free and unattached, it is ])robably a parasite, owing to the fact 

 that it presents marked degeneration in having lost all the abdominal 

 appendages. It is also without eyes and has prehensile legs. I have 

 made it the type of a new family, Colypuridae. 



A few years ago,^ Giard and Bonnier described a peculiar Isopod, 

 Rhahdoehirus incertus, which also lacks abdominal appendages. The 

 abdomen, however, is not inserted under and covered by the last thoracic 

 segment, as is characteristic of the present type. Rhahdoehirus incertus 

 also differs in having all seven segments of the thorax free, well devel- 

 oped antennae, and a differentiation in the thoracic legs, which are not 

 prehensile, the three anterior pairs and the seventh pair being very much 

 shorter, about half as long as the fourth, fifth, and sixth pairs. Giard 

 and Bonnier were unable to place it in any of the known families of the 

 order. I propose for this form the family Rhabdochjridae. 



COLYPURIDAE. 

 ColypTirus, gen. nov. 



Head coalesced with the first thoracic segment. The following six 

 thoracic segments free, the first four free segments increasing gradually 

 in width backward. Seventh thoracic segment, or sixth free segment, 

 longer than the others and rounded posteriorly. 



1 BuU. Soc. Ent. France, 1898, No. 9, pp. 198-200. 



