166 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



"Telson triangular, about two-thirds as long as broad, lateral mar- 

 gins somewhat excavated, apex narrow, rounded. 



"Seventeen specimens from stations 6062 and 6063, 25 to 75 fathoms. 

 Largest 8.5 mm. by 3.8 mm. ; smallest 5.5 mm. by 2.5 mm." MOORE." 



Family VIII. MG1DM. 



Bod}^ more or less broad, flattened. 



Head transverse. 



Segments of thorax with epimera distinctly defined on alt the seg- 

 ments, with the exception of the first. 



. Abdomen composed of six well-defined segments, the last segment 

 ciliated on the posterior margin. Uropoda together with the terminal 

 abdominal segment forming a caudal fan. Eyes, when present, usually 

 large. Antennae laterally directed, both pairs furnished with distinct!}' 

 defined, multi-articulate flagella. Peduncle and flagella well defined. 



First three pairs of legs prehensile, last four pairs ambulatory. 



Pleopods serving for swimming and for respiration; furnished with 

 cilia. 



First maxillae with only a single slender masticatory lobe, tipped by 

 short spines. 



Second maxillae broader, terminating in two unequal lobes, armed 

 with recurved teeth. 



Last article of palp of maxillipeds armed with strong recurved teeth. 



Terminal abdominal segment and uropoda furnished with cilia. 



Parasitic forms usually found attached to the skin of fishes. 



ANALYTICAL KEY TO THE GENERA OF THE FAMILY JEfilDM. 



a. Body compact. First two articles of the peduncle of the first pair of antennae 

 more or less expanded. . Frontal lamina large. Maxillipeds with the palp com- 

 posed of five articles. Front of head with median point separating wholly or 

 partly the first articles of the first pair of antennae. Flagellum of the first anten- 

 nae composed of numerous articles. Abdomen compact Genus sEga Leach 



of. Body depressed. First two articles of the peduncle of the first pair of antennae 

 not expanded. Frontal lamina small. Maxillipeds with the palp composed of 

 only two articles. Front of head covering more or less the peduncle of the first 

 pair of antennae. Flagellum of first antennae composed of four to six articles. 

 Abdomen relaxed. 



b. Eyes present. Three anterior pairs of legs with propodus more or less expanded, 

 and armed with spines; dactylus forming a very large and evenly curved 

 hook. Four posterior pairs with the propodus short. Mandibles with the 

 cutting edge expanded inside in a linguiform lamella. Abdomen not much 



narrower than thorax Genus Rocinela Leach 



b' '. Eyes wanting. Three anterior pairs of legs with propodus not expanded ; dactylus 

 abruptly curved in the middle and terminating in a very sharp point. Four 

 posterior pairs with the propodus elongated. Mandibles without linguiform 

 lamella. Abdomen abruptly narrower than thorax. .Genus Syscenus Harger 



Bull. U. S. Fish Commission, XX, Pt. 2, 1902, pp. 169-170. 



