368 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



FIG. 399. IDOTHEA PHOSPHOREA. O, M.VMI.- 



LIPED. x 27J. 6, FIRST ANTENNA, x 15J. 



pair of antennae not dilated, and but little wider than second article. 

 First, second, and third articles about equal in length; fourth article a 

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

 end of the third peduncular article of the second pair of antennae. The 

 basal article of the second antennae 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 flagellum consists of sixteen arti- 

 cles. When retracted, the second 

 antennae extend to the posterior mar- 

 gin of the third thoracic segment. 

 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 about four-fifths 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, carpus and pro- 

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

 bj- a long terminal one with lateral sutures at the base. The terminal 

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

 indication of a rudimentaiy lateral angle. Color usual ly dark green 

 or brownish, with transverse patches of yellow. 



6O. Genus PENTIDOTEA, new genus. 



Flagellum of second antennae multi-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 segments, 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 genus, all agreeing in hav- 

 ing the palp of the maxillipeds composed of five articles. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS PENTIDOTEA. 



a. Terminal segment of body with a deep ernargination at its posterior extremity, 



the post-lateral angles formed being very acute Pentidotea resecata (Stimpson) 



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



