822 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



and somewhat dilated; the second article is nearly twice as long- as the 

 first, and is also somewhat dilated; the third article is as long- as the 

 second, but more slender; the fourth article is almost as long as the 

 third. The flagellum is composed of five articles. The first antenna^ 

 extend to the posterior margin of the first thoracic segment or to the 

 end of the peduncle of the second pair of antenniB. The basal article 

 of the second antenna? is short and is not visible from a doi'sal view^; 

 the second article is about twice as long as the first; the antenna' are 

 geniculate between the second and third articles; the third irticle is 

 about as long as the second; the fourth is twice as long- as the third; 

 the fifth is one and a half times longer than the fourth. The fiagellum 

 is composed of seven articles. The second ante nine extend to the 

 posterior marg-in of the second thoracic segment. The maxilliped has 

 a palp of three articles. The palp of the mandibles is composed of 

 three articles. 



The first segment of the thorax is fused with the posterior portion 

 of the head along- the posterior margin. The lateral portions of the 

 segment are widely expanded and surround the head, the antero-lateral 

 angles extending to the anterior marg-in of the head. The five fol- 

 lowing segments are free, with the lateral parts widely expanded and 

 subequal. The first segment and the last two (the fifth and sixth) are 

 very much shorter in the median longitudinal line than the interme- 

 diate ones. The seventh segment is entirely wanting on the dorsal 

 side. The epimera are not distinct from the segments, but are per- 

 fectly coalesced, with no indication of the place of fusion. 



The abdomen is composed of four segments, the first three of which 

 are short and subequal in length. The lateral parts of the first two 

 are covered by the widely produced lateral parts of the last thoracic 

 segment. The fourth or terminal seg-ment of the al)domen is large, 

 somewhat triangular in shape, with apex obtusely rounded. A little 

 more than one-third the distance from the base to the apex is a sharp 

 tooth on either side, below which the abdomen becomes more attenu- 

 ated. The peduncle of the uropoda arises at this point on tlie ventral 

 side. The peduncle of the uropoda extends to about the middle of the 

 lateral margin of the terminal abdominal segment. The branches are 

 subequal in length and of equal width. They are rounded posteriorly, 

 somewhat crenulate on the lateral margins, and extend a short distance 

 beyond the tip of the tei'minal segment. 



The first pair of legs are subchelate, with propodus greatly dilated. 

 All the other six pairs of legs are ambulatory. In the male the first 

 two pairs of legs are subchelate, the second pair being smaller than 

 the first. There are five pairs of pleopoda, one pair for each of the 

 first three segments; the fourth pair have the outer ])ranch forming 

 an operculum folding over the entire ventral side of the last segment 

 and attached at the anterior end, being- free elsewhere; the fifth pair 

 are concealed under the operculum. 



