CALIFORNIA STALK-EYED CRUSTACEA. 221 



either side; posterior margin with three large spines on either side of the 

 median notch; a rounded denticle between the submedian and interme- 

 diate spines. 



Chili; San Pedro (Bigelow); Santa Catalina Island! 

 Point Mendocino, Calif.! 



Suborder SCHIZOPODA. 



Carapace rather small and generally not covering all the segments of 

 the thorax. Eyes stalked. Mandibles generally furnished with an elon- 

 gated palp. Maxillipeds similar to the succeeding appendages of the 

 thorax which are furnished with well developed exopods. Ova carried 

 beneath the thorax, with or without marsupial plates. Tail-fin well 

 developed . 



Family MYSID^E. 



Carapace small and membranaceous. Pereopods generally of similar 

 form and slender. Branchiae entirely absent. Females with a marsupial 

 pouch. Pleopods generally rudimentary in the female and often so in the 

 male. Inner ramus of the uropods usually furnished with an auditory 

 organ. 



Genus Mysis Latr. 



Body slender. Antennal scale setose on both sides and not ending in a 

 spine. Thoracic legs with the propodi subdivided. Fourth pair of pleo- 

 pods in the male with the outer ramus greatly elongated; third pair of 

 pleopods generally unlike those of the female, the remaining pairs simple 

 and rudimentary as in the other sex. 



Type. M. oculata FABB. 



Mysis costata, sp. nov. 



Rostrum broadly triangular, ending in a spine. Ocular peduncles short, 

 stout, and slightly flattened horizontally. First joint of the antennular 

 peduncle about one-half longer than wide; second joint very short; outer 

 flagellam about twice as long as the inner one and furnished with a few 

 long setffi near the base; the sensory organ of the male is well developed 

 and furnished with a large, dense tuft of long curved hairs. Peduncle of 

 the antennae reaching about to the middle of the acicle but not reaching 

 the tip of the peduncle of the antennules; second joint with a spine 



