180 U.S. NATIONAL MUSEUM BULLETIN 271 



Cheluridae 



Figure 74 



Diagnosis. — Body depressed; segments of urosome immovably 

 fused together, marked ventrally by sutures, segment 3 very large; 

 uropods 1, 2, and 3 radically dissimilar to each other in structure and 

 size; telson foliate, entire; accessory flagellum present; flagellum 

 of antenna 2 clavate, composed largely of one article in the adult. 

 See Corophiidae. 



Description. — Accessory flagellum 1-articulate, stout; flagellum 

 of antenna 2 largely composed of one clavate article; head either 

 bulbous and lacking supra-antennal line, or quadrate and bearing 

 such line; mouthparts basic; coxae short, not overlapping; gnathopod 



1 either feeble and slightly chelate, or large and subchelate; gnathopod 



2 feeble and slightly chelate; uropods dissimilar, uropod 1 composed 

 of normal peduncle and two short rami; uropod 2 composed of foli- 

 aceous peduncle, with or without rami; uropod 3 composed of short 

 peduncle, a greatly enlarged outer ramus and a scale-like or no 

 inner ramus; telson entire. 



Relationship. — Unlike the Cheluridae, uropods 1 and 2 of the 

 Corophiidae are similar to each other, the second antennal flagellum 

 is distinctly multiarticulate, the third urosomal segment, although 

 occasionally fused to the others, is never greatly enlarged, and the 

 third uropods are never immensely enlarged as in the Cheluridae. 



Key to the Genera of Cheluridae 



1. Uropod 3 bearing a scale-like inner ramus (fig. 74Z) Chelura 



Uropod 3 lacking an inner ramus 2 



2. Uropod 2 with two rami (fig. 74/;), gnathopod 1 large, subchelate (fig. 74n). 



TropicBelura 

 Uropod 2 lacking rami (fig. 74o), gnathopod 1 small, slightly chelate (fig. 74/i). 



Nippochelura 



Genera of Cheluridae 



Chelura Philippi 



Chelura PhiHppi, 1839.— Stebbing, 1906. 



Type-species: C. terebrans Philippi, 1839 (monotypy). See Sars, 

 1895. 



Supra-antennal line absent except in defining the lateral ocular 

 lobes; gnathopods small; uropod 2 with two rami; uropod 3 with 

 small inner ramus. Species: 1, circumamphiboreal, littoral, bores 

 wood. 



