368 



BULLETIN 'A, UNITED STATES NATIONAL MUSEUM. 



pair of anteiiiuv not (lilated, and hut little wider than second article. 

 First, second, and third articles about e([ual in length; fourth article a 

 little longer than any of the others. The first antenna' extend to the 

 end of the third peduncular article of the second pair of antenna\ The 

 basal article of the second antennw is almost inconspicuous; the sec- 

 ond and third articles are subequal; 

 the fourth is about one and a half 

 times longer than the third; the fifth 

 is a little longer than the fourth. 

 The Hagellum consists of sixteen arti- 

 cles. When retracted, the second 

 antenna? extend to the posterior mar- 

 gin of the third thoracic seg'ment. 

 The maxillipeds have a palp of four 

 articles. 



The segments of the thorax are 

 subequal, except the first, which is 

 shorter in the median dorsal line. 

 The epimera of the second and third 

 segments occupy the anterior two- 

 thirds of the lateral margin: the epi- 

 meron of the fourth segment occupies a))Out four-tifths of the lateral 

 margin; the epimera of the last three segments occupy the entire 

 lateral margin and are increasingly broader at the posterior end. 



The legs are more or less similar in structure, and are furnished 

 with hairs along* the inferior margin of the merus, cai"pus and pro- 

 podus. The tirst two segments of the abdomen are short, followed 

 b}' a long terminal (me with lateral sutures at the ])ase. The tei'minal 

 segment tapers to a pointed extremity, on either side of which is an 

 indication of a rudimentary lateral angle. Color usually dark g'reen 

 or brownish, with transverse patches of yellow. 



Fig. 399. — Idothea phosphorea. a, Maxil^ 

 LiPED. X 27|. &, First ANTENNA. ■ l-'il. 



60. Genus PENTIDOTEA, new genus. 



Flagellum of second antennte nnilti-articulate. Maxillipeds with a 

 palp composed of five articles. Epimera of all the segments of the 

 thorax with the exception of the first distinctly separated from the 

 segments. Abdomen composed of three seg-ments, with a suture line 

 on either side of the terminal segment at the base, indicating another 

 partly coalesced segment. 



There are as yet but four species of this g-enus, all agi-eeing in hav- 

 ing the palp of the niiixillipeds composed of five articles. 



ANALYTICAI, KEY TO THE SPECIES OK THE (lEXIS PENTIDOTEA. 



a. Tcrniiiial st'{z;iiic'iil: of body with a <U'e|» ciiiariiiiiatioii at its jxjstcrior extremity, 



tlie post-lateral anj^des formed beinj^ very acute Pi-iitidotea resecata (ytimpsoii) 



a'. Terminal segment of body not, emarginate at its posterior extremity. 



