CRUSTACEA MALACOSTRACA. III. 27 



The thoracic segments laterally produced in plates (PI. II, figs. 1 a — 1 b); first, sixth and seventh 

 segments each with a single lobe; in the four other segments each plate is divided into two lobes by 

 a triangular incision. — Thoracic legs of middle length; first pair in both sexes (figs, id and 1 e) 

 terminate in a fully developed, slender chela; the other pairs have the seventh joint robust and of 

 very moderate length (fig. 1 f), the claw somewhat strong and the accessory claw small and slender. 



The abdomen differs from Ianira in having the part between the uropods very convex and 

 protruding as a transverse plate. — The median lamella of the male operculum (fig. 1 i) is broad, 

 tapering to somewhat from the end, and then scarcely widening; the copulatory organ reaches about 

 to the end of its pleopod (PI. I, fig. gd); the female operculum (fig. 1 h) rounded behind. — The uropods 

 (fig. 1 g) consist of two joints, the first quite short and hidden beneath the dorsal plate of the abdomen, 

 the second somewhat large. 



Remarks. Katianira shows some resemblance to Ianira, but differs abundantly in having the 

 antennae short, the molar process of the mandibles tapering, only four joints in the "palp" of the 

 maxillipeds, a real chela on first pair of legs, and the uropods without exopod. 



Only a single species is known. 



12. Katianira chelifera n. sp. 

 (PI. I, figs. 9 a— 9 d; PI. II, figs. 1 a— 1 i.) 



Description. Body about two and a half times as long as broad (fig. 1 a), with the surface 

 smooth. — The lateral margins of the head (fig. 1 c) have a longer or shorter portion finely serrate; 

 labrum is visible from above. — The antennulse nearly reach the posterior margin of first thoracic 

 segment; the first peduncular joint is slightly longer and thicker than the second; flagellum about half 

 as long again as the peduncle, 5-jointed, with second joint about as long as the two following joints 

 together. — Antennae conspicuously shorter than the antennulae (fig. ic); flagellum shorter than the 

 peduncle, 4-jointed. 



Thoracic segments peculiarly adorned, as all the free margins are serrate, being closely set with 

 numerous small processes about equal in length (fig. ib); the lateral lobes of the segments are sub- 

 acute, terminating in a conspicuous, articulated spine; on second to fourth segments the lateral lobes 

 of each segment differ much in size and shape, the anterior lobe being considerably shorter and several 

 times narrower than the posterior; on the fifth segment the anterior lobe is about as long as the 

 posterior. — The chela of first legs in the female (fig. 1 e) about four times, in the male (fig. id) more 

 than four and a half times as long as broad ; the fingers are considerably shorter than the hand, equal 

 in length, somewhat curved near the end, acute, and the movable finger is conspicuously thicker than 

 the other. 



The abdomen (figs. 1 a, 1 g, 1 i) about as long as broad, on each lateral margin with five or 

 six low protuberances, each terminating in a thick, conspicuous spine; besides, the intervals between 

 the three anterior spines adorned with some minute saw-teeth. The protruding lobe between the 

 uropods is less than twice as broad as long, and its moderately convex hind margin has 6—8 small, 

 thin spines. — The operculum is placed somewhat backwards, in the female reaching nearly to, in the 

 male even slightly overreaching, the posterior margin of the abdomen, In the male (fig. 1 i) each 



