222 CALIFORNIA ACADEMY OF SCIENCES. 



external to the base of the acicle; acicle narrow, tapering slightly towards 

 the narrowly rounded tip and ciliated on both margins. Trunk of the 

 mandibles very short and thick; penultimate joint of the palp widest a 

 short distance from the base, whence it tapers to the distal end; second 

 joint narrow, shorter than the preceding one, thickly setose, and having 

 a large, curved, claw-like seta at the tip. The three pairs of maxillipeds 

 end in a claw, the last joint of the third pair five-jointed; the propodi of 

 the succeeding thoracic appendages are 5-7-jointed and end in a claw. 

 Pleopods of the female simple and rudimentary. First three pairs of 

 pleopods in the male simple and rudimentary, as in the female, and of 

 similar form and nearly equal size; fourth pair with the exopod long, 

 slender, smooth and curved, extending backwards beyond the tip of the 

 sixth abdominal segment, the endopod short and furnished with long, 

 plumose setae; fifth pair of pleopods similar to, but slightly longer than 

 the first three pairs. Telsou very narrowly triangular, channeled above, 

 and tapering to the narrow tip which is armed with strong spines; the 

 margins are armed with strong spines, between which are several smaller 

 ones. Inner caudal lamella narrow, widened at the base where the audi- 

 tory organ is situated, rounded at the tip, and about equalling the telson; 

 outer lamella about one-fourth longer than the inner one. The first 

 abdominal segment is crossed with three and the following segments with 

 two transverse ridges; first ridge on the sixth segment with a prominent 

 median spine, second ridge with a pair of small median spines, and at the 

 posterior margin of the segment there is a small median spine with a 

 rounded lobe on either side. Two pairs of marsupial lamellae. 

 Length, 10 mm. 



Numerous specimens taken in a tow net at San Pedro, 

 Calif., July, 1896. 



Collection University of California. 



Genus Neomysis Czerniavsky. 



Very closely allied to Mysls, from which it differs in having the long, 

 narrow, antennal scale, which is setose on both margins, end in a sharp 

 spine. 



Type. — N. vulgaris (Thompson). 



X Neomysis mercedis Holmes. 



Neomysis mercedis Holmes, Proc. Cal. Acad. Sci. (2), Vol. VI, 1897, p. 199, 

 PI. XIX, figs. 1-10. 



Rostrum rounded. Acicle narrow, elongated, tapering gradually to an 

 acute tip, and furnished with thickly set, plumose setse on both margins. 



