SOUTHWELL ANOMUR A 117 



P. obesulus: P. biunguiculatus : 



(1) Median frontal projection (1) Median frontal projection 



obtusely rounded and prominent and acute, 



but little projecting. 



(2) Ambulatory dactyli tri- (2) Ambulatory dactyli bi- 



unguiculate. unguiculate. 



I am now convinced that these differences are sufficiently stable to be specific 

 a conclusion arrived at after examining some hundreds of specimens of P. obesulus. 

 At the same time I would here remark that the aforesaid points of difference are 

 liable to a little variation. In one or two adult specimens of P. obesulus. with 

 typically triunguiculate dactyli, the rostrum was scarcely obtuse, whilst in others 

 it was almost straight. Again, one specimen was found with two of the dactyli 

 on the walking legs typically biunguiculate, and in the other specimens the small 

 proximal claw itself was noted to vary in size. 



Poly onyx hendersoni, n. sp. (18) Plate, figs. 6-9. 



Carapace more convex from front to back than from side to side, broader 

 than long the greatest breadth being anterior smooth dorsally, but lineolate 

 along the posterior lateral borders. Rostrum sub-acute, rounded, only slightly 

 projecting, and not visible in a dorsal view. Chelipedes variable, the left or right 

 being the larger. Merus with a small tuberculated lobe on its distal internal face. 

 Carpus as broad as long, strongly tuberculated, its internal edge produced into a 

 rounded lobe bearing a few blunt teeth, and having a ventral entire carina. Propodus 

 small proximally, widening distally, the length slightly greater than the breadth, 

 tuberculated dorsally, smooth ventrally. Fingers curved or not, with a hiatus 

 between them when closed, or not. The ambulatory dactyli are four-clawed, the 

 terminal claw being slightly longer than the penultimate one, and the two proximal 

 ones being minute. Ambulatory legs bear short, matty hairs on their anterior 

 edge. 



Length of carapace, G mm. ; breadth ot carapace, 8 mm. 



Natural colour : varying shades of brick red. 



Locality : South of Adams Bridge, Ceylon, eight and a half fathoms. 



Found along with P. obesulus inhabiting the cavities of sponges, dead coral 

 and rock. Several specimens, males and females, many of the latter bearing eggs. 



This species is the one doubtfully referred to as Polyonyx tuberculosus by 

 Henderson in his " Indian Carciiiology." After giving a short description of it 

 without naming it, he says, " this species is certainly distinct from P. obesulus 

 or P. biunguiculatus, and as de Man represents his species with the carpus smooth 



above, and with very few tubercles present on the hand, our specimens may also 



K 2 



