(20) 



P. exilipes, Stimpson. Rostrum nearly straight, seven or eight teeth 

 above, one or two below. Hand of second pair of feet about two-thirds as 

 long as carpus. 



FAMILY MYSIDAE. 



Feet more than five pairs, slender, often bearing palpi, none chelate, 

 usually rudimentary on the abdomen. Grills wanting. 



Genus Mysis. 

 Six pairs of thoracic feet, each with two many-jointed branches ; three 

 pairs of maxillipeds (12). Inner antennae with two flagella. Fourth pair of 

 abdominal legs in male very long, styliform, directed backwards. 



M. rdicta, Lovem. Cephalo-thorax about one- third total length, 

 broader behind than before. Pedicel (lo) of inner antennae a little longer than 

 the eyes, three-jointed, first joint about as long as second and third together. 

 Inner flagellum shorter and more slender than outer. 



ORDER AMPHIPODA. 



Body commonly compressed, of fourteen segments ; thoracic segments 

 not consolidated, eyes sessile if present. Gill plates thoracic. 



FAMILY ORCHESTIDAE. 



Upper antennae shorter than lower, no secondary flagellum (14). No 

 palpus to mandible. Epimera (15j large. Last pair of abdominal legs not 

 branched. 



Genus Hyalella. 



First two pairs of feet sub-chelate (16), the second the larger; upper 

 antennae as long as peduncle of lower; telson (17), short, stout, entire ; palpus 

 of maxillipeds five-jointed; first pair of maxillae with very short one-jointed 

 palpi. 



H. dentata, Smith. First and second abdominal segments with a 

 prominent tooth on middle of hind margin, second hand of male about three 

 times as broad as first, flagellum of lower antenna commonly but little 

 longer than that of upper. 



FAMILY LYSIANASSIDAE. 



Body little compressed, first two pairs of feet small and weak, epimera 

 of first four segments very deep. 



Genus Pontoporeia. 



Upper antennae with short secondary flagellum ; first two pairs of legs 

 very short, the first sub-chelate, the second not, seventh pair with basal joint 

 very large. 



P. hoyi, Smith. First pai-r of hands with one to three small slender 

 spines at tip of closed claw. About seven elongated papillae on the second 

 to fifth segments of the sternum (18). Upper antennae short, about as long as 

 head and first three thoracic segments; flagellum about nine-jointed. 



P. filicornis, Smith. Upper antennae reaching nearly to tip of ab- 

 domen, flagellum of about thirty-three joints, the terminal ones very long 

 and slender. Secondary flagellum of four segments. 



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