226 CALIFORNIA ACADEMY OF SCIENCES. 



the margins of which are closely set with small spinules; sides of the 

 telson armed with spinules throughout their length. Inner caudal lamella 

 about three-fourths the length of the outer one, but much longer than the 

 telson and scarcely widened at the bane where the small auditory organ is 

 located. Both lamellio are strongly ciliated and rounded at the tip. 

 Length, one-half inch. 



A single specimen taken at San Pedro, Calif., 

 June, 1896. 



Collection University of California. 



Genus Mysidopsis Sars. 



Carapace comparatively small and not covering all the thoracic segments. 

 Antennal scale lanceolate, setose on both edges, with a short apical articu- 

 lation. First and second thoracic appendages powerfully developed; legs 

 unequal, comparatively short and stout, the propodal joint divided into 

 three articulations, the terminal one having a slender setiform claw. 

 Pleopods in the male all natatory. Telson comparatively short, the apex 

 entire or cleft. 



Type. M. didelphys (NORMAN). 



Mysidopsis elongata, sp. nov. 



A small, slender species with a 1 ong, narrow, somewhat depressed abdo- 

 men. Rostrum rounded. Eye-peduncles reaching about to the middle of 

 the antennal scale. In the stout antennular peduncle of the male the first 

 joint is nearly as wide as long, the second joint much wider than long, and 

 the third somewhat longer than wide and furnished with a well developed 

 sense organ below and a foliate appendage on the inner side. In the 

 more slender peduncle of the female the first joint is over twice as long as 

 wide, the second longer than broad, the third nearly as long as the first 

 and devoid of the appendage found in the male; the inner flagellum in 

 both sexes is shorter than the outer one, \yhich does not attain half the 

 length of the body. Antennas short, the acicle narrow, tapering, but not 

 ending in a spine, and having both edges fringed with plumose setae; ped- 

 uncle slender and about two-thirds the length of the acicle. The pleopods 

 of the female are small, slender and uniramous, while those of the male 

 are large, biramous, and of similar form. Sixth abdominal segment about 

 as long as the two preceding ones combined. Telson not one-half as long 

 as the preceding segment and not reaching beyond the middle of the 

 inner ramus of the uropods; its general form is triangular, but the sides 

 converge more strongly in the basal half; the tip is broadly rounded and 



