no. 1654. AMPHIPODA FROM WEST NORTH AMERICA— HOLMES. 533 



N. assimilis (Sars) it differs in the more rectangular hands on the 

 gnathopods; from N. bairdi (Boeck) it differs in the shape of the 

 hands which are oval in that species as well as in the size of the 

 hands which are relatively much smaller. 



Genus ACANTHOPLEUSTES," new. 



Rostrum minute or absent. First antennas elongate, with small 

 accessory flagellum. Upper lip evenly rounded, entire. Mandibles 

 with elongated, narrow three-jointed palp situated nearly opposite 

 the well-developed molar tubercle; secondary plate on both mandibles. 

 Lower lip with inner lobes fairly well developed. First maxillae 

 short, the inner plate broad, distal ly rounded and armed with a few 

 plumose setae; outer plate but little longer than the inner and armed 

 with branched spines; palp two-jointed, the distal margin armed with 

 stout spines. Second maxillae with nearly equal oblong setose lobes. 

 Maxillipeds with inner plates small, armed distally with three spine 

 teeth ; outer plates small, not reaching beyond middle of antepenulti- 

 mate joint of palp, devoid of teeth, but furnished distally and along 

 inner margin with long ciliated spine-like setae; last joint of large palp 

 a strong claw. 



Gnathopods similar, fairly well developed, subchelate, side plates 

 two to four pointed below. Last three peraeopods rather long, with 

 narrow basal joints. First three abdominal and some of the posterior 

 thoracic segments produced posteriorly into teeth or spines. Rami 

 of uropods lanceolate, those of the last pair broader than the others. 

 Telson small, entire or slightly emarginate, and furnished with a 

 prominent keel on the lower side. 



Type. — A. annectens, new species. 



This genus does not fall strictly within the limits of any of the 

 families of Gammaridea, as they are defined by Sars or Stebbing. 

 It is very close to the Paramphithoidae as limited by Sars, but the 

 antenna 1 have a secondary flagellum, and the upper lip is entire. 

 Stebbing defines the Paramphithoidae differently from Sars, includ- 

 ing, besides the genus Paramphthoe, the genera Avhich Sars places in 

 the family Epimeridae, and making out of several other genera wdiich 

 Sars placed in the family Paramphithoidae, the new family Pleustidae. 

 It could be placed in the Calliopiidae without doing violence to the 

 definition of that family as given by Stebbing. Sars has commented 

 on the resemblance of the Calliopiidae and Paramphithoidae and the 

 present genus seems to occupy a position in some respects intermediate 

 between these two families. The rudimentary rostrum, the presence 

 of structures resembling calceolae on the antennae and the entire upper 

 lip, are features more in accord with the Calliopiidae, while the spiny 

 dorsum, the pointed coxal plates, the ventrally keeled telson, the nar- 



«From the Greek words axavSa, spine, and Pleiistes, a related genus of amphipods. 



