74 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



The first segment of the thorax is 2 mm. long; the second and third 

 are subequal and each is 3 mm. in length; the fourth segment is 4 

 mm. long; the fifth segment is 3 mm. long; the sixth is 2 mm.; the 

 seventh is 1 mm. in length. The segments are long and narrow and 

 have no epimera separated off. The second and third segments have 

 each at the anterior end two small tubercles, one on either side of the 

 median line. The fourth, fifth, and sixth segments have each a small 

 depression at the anterior end in the median line. 



The abdomen is short, being only 4 mm. in length, or less than one- 

 sixth the entire length of the body. The first six segments are indis- 

 tinctly defined, and are more or less fused in the median dorsal line. 

 The seventh and last segment or telson is triangular in shape with apex 

 acute. The peduncle of the uropoda is broad and extends two-thirds 

 the length of the terminal abdominal segment. The inner lateral 

 branch is small and placed at the posterior end of the peduncle and 

 extends the remaining third of the length of the terminal abdominal 

 segment, reaching the extremity of that segment. The outer or supe- 

 rior branch is dorsally placed and arches over the telson, meeting the 

 branch of the opposite side in the median dorsal line; it is about twice 

 as broad as long and is posteriorly truncate. 



The first three pairs of legs are prehensile, the first pair being much 

 the larger and stouter. The four remaining pairs are ambulatory. 



CALATHURA CRENULATA Richardson. 



Calathura crenulata RICHARDSON, Proc. U. S. Nat. Mus., XXIII, 1901, pp. 509-610. 



Localities. Between Nassau and Andros Island, Bahamas; Cape 

 Catoche, Yucatan. 



Depth. 21 fathoms. Found in gulf weed. 



Head half as long as first thoracic segment, frontal margin with 



small median point 

 and prominent lat- 

 eral angles. Eyes 

 large, distinct, and 

 very black. First 

 pair of antennae 

 more than twice as 



long as the length of the head; flagelluni about seven- 

 teen jointed. Second pair of antennae somewhat longer 

 than first pair, with joints of flagellum stouter; flagel- 

 lum about twenty-three jointed. 



First six thoracic segments long and narrow; sec- 

 ond segment narrower posteriorly than anteriorly; FIG. 59. --CALATHURA 

 last segment very short, one-third shorter than pre- CKENULATA. 

 ceding segment. Abdomen with all the segments distinct. Terminal 



FIG. 58. CALATHURA CRENULATA. HEAD. 



