650 CRUSTACEA. 



organ of motion. The legs terminate in a few setules, without a 

 claw. 



Segments of abdomen naked. Last segment narrowing a very little 

 towards apex. The seta-like processes either side of extremity are 

 close appressed to the segment, and do not project beyond the short 

 apical spinules. Caudal lamellsc a little shorter than the segment, the 

 outer not jointed. Base of the caudal appendages a little spinose on 

 the margin ; long hairs on inner side and end of outer, and on both 

 margins of inner. 



Liver many-lobed, somewhat botryoidal. Abdominal natatory ap- 

 pendages nearly as in the Euphausiae. 



FAMILY II. MYSID^E. 

 SUBFAMILY I. MYSIN^E. 



THE genera here included differ most obviously in the presence or 

 absence of a scale at apex of base of inner antennae; in the number 

 of thoracic feet, some of the anterior sometimes acting as maxillipeds 

 and differing from the follovung, in the character of the articulation 

 of these legs; in the greater or less development of the abdominal 

 appendages ; in the caudal segment and lamellae. The posterior 

 thoracic legs are never wanting, as in the Euphausiae, and when the 

 number of pairs is but six, it arises from the pairs anterior being small 

 and properly maxillipeds in character. In the genus Mysis the pedi- 

 form branch of the thoracic legs has the tarsus indistinctly multiarti- 

 culate, a peculiarity not yet observed in other genera. 



GENUS PROMYSIS. 



Antennae, internee flagellis dudbits lamindque ollongd confectce. Oculi 

 symmetrici, breves. Pedes thoracis duodecim et tar so aim pi ice, tiiignicu- 

 lato. Maxiliipedes quatuor pediformes, pare secundo et paribus pedum 



