266 Capt. A. C. MacGilcLrist on Decajmd Crustacea 



(2j The four tcetli of the front are not equally aeutc ; 

 the inner two are long and acute, bnt the outer, although 

 projecting well forward, are broad, blunt, and rounded at 

 the end. 



(3) The teeth on the posterior bor(;er resemble more 

 those of P. serripes in being broad and blunt. 



(4) Eetwcen the sharp little tubercles on the arcolajof the 

 carajjace the surface is not smooth, but is densely and finely 

 granular. 



Only a male (9 mm. long and 11 mm. broad) was obtained, 

 Sta. 291, Persian Gulf, 49-48 fathoms. 



Fam. Ptenoplacidae. 

 Ptenoplax, Alcoek and Anderson. 



Ptenoplax dentata, sp. n. 



Carapace very flat and depressed, transversely oval, and its 

 antero-lateral borders dentate. Surface very finely granular 

 beneath a short furry coating; front and antero-lateral 

 borders with much longer hairs. Front proper is extremely 

 narrow, about ^^ greatest breadth of car;:pace ; in length 

 about ^ greatest breadth of carapace, deflexed, and with its 

 tip free, horizontal, and tapering to a point — not expanded 

 and bilobcd as in P. notopus. Orbital and frontal borders 

 together are slightly more than ^ greatest breadth of eara- 

 l^ace; antero-lateral border is long, convex, and armed with 

 3 teeth (besides the supraorbital tooth) ; postero-lateral 

 border is convex and smooth ; posterior border proper is 

 straight and raised. Regions of carapace are fairly well 

 defined. The branchial regions are much depressed and less 

 inflated than in P. notopus. The two transverse sutures so 

 conspicuous and sharply defined in P. notopus are not 

 present, but the blunt, convex, transverse ridges in which 

 the sutures exist in P. notopus are here quite as prominent 

 and similarly situated, the anterior passing across the cara- 

 pace between the penultimate teeth of the autero-lateral 

 borders. 



The side-walls of the carapace are also finely granular 

 and meet the dorsal surface almost at right angles. The 

 pterygostomial regions are deeply grooved and the sternum 

 is pentagonal, as in P. notopnis, their surface being finely 

 granular. 



