116 OKHAMANDAL MARINE ZOOLOGY REPORT 



Polyonyx, STIMPSON. 



Stimpson (34), Henderson (19), Henderson (18), Southwell (32). 



Carapace suborbicular, and convex, the breadth slightly greater than the length. 

 Front but little produced, with an almost straight margin. First joint of the 

 antennular peduncle smooth. The corresponding joint of antennal peduncle greatly 

 elongated. Eyes of small size. Chclipedes smooth with the merus broad. Dactyli of 

 the ambulatory limbs short and furnished with two or more well- developed claws. 



Polyonyx obesulus (WHITE). Plate, fig. 5. 



Southwell (32), Henderson (18), Henderson (19). 



Carapace smooth and convex, the breadth slightly greater than the length. 

 Rostrum very slightly developed, obtusely rounded and deflexed in such a way that 

 it is not seen in a dorsal view. First segment of the antennal peduncle long. 

 Chelipedes equal, or the right or left the larger. Outer surface of the hand smooth. 

 Merus of the chelipedes has its internal distal angle produced into an entire lobe. 

 Carpus longer than broad. Propodite as broad as long. Fingers gaping or not, and 

 mostly curved. The ambulatory dactyli are triunguiculate. 



Localities : (1) Kiu, Okhamandal, low water ; (2) South-west coast, Beyt 

 Island. One specimen from each locality. 



Breadth of carapace, 8 mm. Natural colour : brownish-grey, turning red in 

 spirit. 



Previously recorded from : Amboina, de Man ; Singapore, Walker; N. Australia, 

 Miers ; Ceylon Pearl Banks, Southwell ; Madjicosima Is., White ; Flinders Passage, 

 Henderson. 



This species is closely related to P. biunguiculatus, and De Man suggested 

 their union into one, an idea, however, which was opposed both by Miers and 

 Henderson. 



In a former paper on the Anomura of the Ceylon Pearl Banks, I remarked that 

 P. obesulus and P. biungwculatus " seem so closely related that it is difficult to 

 believe that they are distinct. Some of our Ceylon specimens seem intermediate 

 in their character." 



Since the preceding statement was written I have had many opportunities of 

 examining numbers of fresh specimens from the Ceylon Pearl Banks, where the 

 species occurs plentifully in shallow water, usually inhabiting the large exhalant 

 apertures of a species of Hippospongia, or found hidden in the cavities of rock or 

 dead coral. 



The two principal points in which P. obesulus differs from P. biunguiculatus 

 may be summarised thus : 



