1907.] CRUSTACEA OF THE THIRD TANGANYIKA EXPEDITION. 273 



dredged among shells in about 10-15 fathoms. Also obtained in 

 rather shallower water, but seldom in less than about 8 fathoms. 



Pembe (east coast) : among shells dredged in aboiit 10 fathoms. 



Kirando (east coast), 1/12/04: dredged in about 10 fathoms. 

 Among these, a curiously blotched and not spotted individual. 



Platythelphusa conculcata, sp. n. (Plate XVII. figs. 2 & 4.) 



Description. — Carapace extremely flattened, extending laterally 

 less than an orbit's breadth beyond the external oi-bital angle. 

 The whole body remarkably thin in appearance. Antero-lateial 

 margins shorter than postero-lateral, with which they are almost 

 directly continuous. Three spines on antero-lateral margin, in 

 addition to that at the external orbital angle. Regions and sutures 

 very ill-defined. Lateral regions exhibit a few small granular 

 ridges. Front more than one-third the width of the carapace, 

 margin spinuliferous and with a sharp spine at each extremity. 

 8ub-orbital spines j)rominent ; a small spine on the descending 

 process of the front. Orbits of moderate size, "18 width of cara- 

 pace ; orbital margins perlated. Eyes and peduncles rather large. 

 Chelipeds in the male subequal ; merus trigonous, with distally a 

 sharp spine on the anterior margin, and a small blunt spine on 

 the ventral margin ; carpus with two spines on inner margin, two 

 on outer margin, and one above the point of articulation with the 

 hand. Fingers distally meet closely in a sharp cutting-edge, 

 while proximally there are uniform teeth of moderate size. 

 Fingers of the larger chela (Plate XVII. fig. 4) have a few larger 

 teeth proximally. Ambulatory legs long and slender ; the anterior 

 margin of the merus, in each case, produced distally into two 

 sharp spines, of which the terminal one is inconspicuous on the 

 first and fourth legs. Colour (in spirit) yellowish brown, with 

 darker reddish-brown spots. 



Dimensions as follows : — 



Male (probably adult) : j^j^_ 



Length of carapace lO'O 



Breadth of carapace 11 "9 



Fronto-orbital width 9" 1 



Width of front 5-0 



Remarks. — It is unfortunate that we possess only a single 

 specimen of this species, which appears nevertheless to be quite 

 well marked. In size it is still smaller than P. maculatct, while 

 the much flattened carapace and remarkable thinness of the body 

 (whence the name) at once arrest the attention. The great 

 development of spines is also striking, there being two additional 

 ones on the outer margin of the cai-pus of the cheliped and the 

 same number on the anterior margin of the merus of the ambula- 

 tory legs. 



Occurrence. — The only specimen obtained was associated with 



