424 CEYLON PEARL OYSTER, REPORT. 



the lateral production of the outer angle of the merus of the external maxillipeds ; 

 additional differences from the same genus concern: (1) ratio of fron to-orbital 

 breadth -=- C. b. ; (2) ratio of frontal b. -=-C.b. ; (3) the more ventral position of the 

 orbits ; (4) eyes, though very small, are distinct ; (5) direction of fold of antennules ; 

 (6) relations of basal antennal segment and orbital hiatus (associated, no doubt, with 

 more ventral position of orbit) ; (7) the markedly plumed antennal flagellum. 

 Characters (4) and (5) approach the condition found in TypKlocarcinus ; (2) and (3) 

 are intermediate between the latter genus and Xenophthalmodes. 



Mertonia lanka, n. sp. Plate I., fig. 11, a, b. 



Locality : Gulf of Manaar, two specimens ( ? and 6 ). 



Description .CI. = 4 in S, 4'5 in ? ; C.b. = 5'5 in 6, 6 in ?. 



Carapace has practically smooth surface, polished, with some irregular dimpling ; 

 its free edges fringed with longish silky hairs; C.b. -j-C.L = 1"37 in cf, 1"33 in ; 

 frontal b.H-C.b. = 0"27 in 6, 0"28 in ? ; fronto-orbital b.-S-C.b. = 0'64 in S, 058 in ? ; 

 front strongly declivous and decidedly bilobed. 



Orbits elongated; long diameter of orbit -j- C.l. = 0"25 in 6, 0"28 in ?. 



The antennal hairs are numerous and long ; antennal flagellum 1. -5-C.l. = - 5 in 6 . 



The buccal cavern increases slightly in breadth anteriorly ; the merus of the 

 external maxilliped has its length and breadth about equal (the measurements taken 

 along the middle line in each case) ; its outer border somewhat convex ; its antero- 

 lateral angle produced and rounded ; the ischium is not much longer than broad ; its 

 breadth is as that of the merus ; a space is left between the ischia and a larger one 

 between the meri (see PI. I., fig. 11, a). 



Chelipeds about same length as walking leg 4 ; hands sub-equal ; inner angle of 

 wrist acuminate ; upper and lower edges of hand sharpened, its surfaces polished, 

 with some dimpling ; the edges of the chelipeds are fringed with silky hairs, these 

 are long on the wrist, shorter on the hand. Walking legs fringed with silky hairs. 



Scalopidia spinosipes, Stimpson, 1858 A.6, p. 325. 



Locality : Gulf of Manaar, one specimen. 



Description: A young male, C.l. = 575 ; C.b. -=-C.l. = L30. 



Pinnoteres margaritiferae, n. sp. Text-fig. 10, 10 a. 



Locality : Pearl banks, Gulf of Manaar, one specimen. 



Description: An adult male. C.l. = 5 '25. 



Carapace well calcified, circular, smooth, and polished ; seen under lens to be 

 pitted, more markedly so towards the margins ; it is flattened a good deal, though a 

 little convex ; its margins are rounded and ill-defined. Front produced, with straight 

 anterior border in dorsal view ; its tip is really, however, deflexed acutely, and its true 

 anterior border, seen in anterior view, is obtusely pointed. Eyes small, well pig- 

 mented ; not entirely visible in a dorsal view of the animal. Propus of external 



