176 University of California Publicatio)is in Zoology [Vol. li 



end obtuse. Each ramus of fourth pair of pleopods with peculiar 

 setae; the endopod (fig. Ic, en) terminates in two strong, naked, 

 spiniform setae, the other seta almost straight, about as long as 

 the sum of the three distal joints, the inner seta distinctly shorter 

 and less thick than the outer and somewhat angularly bent before 

 the middle; the exopod terminates in two setae (fig. le, ex.), one 

 very short, while the other is nearly as long as the long seta on 

 the endopod, naked, robust, and somewhat before the middle 

 strongly bent in a very peculiar way. These setae are quite 

 similar in both uropods of the fourth pair. Finally the inner 

 angle of the penultimate .joint has a nearly straight, naked, 

 strong seta scarcely as long as the long terminal seta. 



Uropods moderately slender (fig. Id). The exopod over- 

 reaches conspicuously the endopod ; its proximal joint is almost 

 three times as long as the distal, with fourteen or fifteen spines 

 occupying somewhat more than half of its outer margin; distal 

 joint not fully twice as long as broad. Telson somewhat less than 

 three times as long as broad, reaching a little beyond the articu- 

 lation of the exopod; along a little more than the distal half 

 each lateral margin has an arrangement of spines nearly as in 

 S. inornata, as above nine or ten long spines are distributed so 

 that proximally four or three shorter spines are found in each 

 interval between two long spines, while distally three or two 

 (or only one) are found in each interval (fig. le). The terminal 

 margin of the telson has three somewhat small spines placed 

 between the single pair of very long and strong spines. 



Length of both sexes, 9 millimeters. 



Remarks. — The male of Siriella pacifica differs from all other 

 species of Siriella hitherto described, excepting S. anomala, by 

 having distal setae on both third and fourth pairs of pleopods 

 modified, but it differs abundantly from the last named species 

 in having the setae modified not only on the endopods but also 

 on the exopods of these pleopods, in the shape of the antennal 

 squama of the exopod of the uropods, etc. The female may be 

 separated from those of S. inornata, S. media, etc., by its some- 

 what smaller eyes. 



