216 DR. MALCOLM SMITH ON 



Rana doricv, was the first to be described. It is the simplest 

 of the group, in that the head of the male undergoes no special 

 changes. In the other members the male head, as it arrives at 

 maturity becomes markedly enlarged. This increase in size is par- 

 ticularly noticeable on the lower surfaces of the mandibles, in the 

 enlargement of the masseteric and depressor muscles, in the greater 

 size of the tympanum, and in the increased width of the interorbital 

 region. A bony tooth-like process also develops in the lower jaw on 

 either side of the symphysis. 



In addition to these changes R. macrognathus and R. pileata 

 develop a rounded swelling upon the top of the head, commencing at 

 the interorbital region and extending backwards towards the occiput. 

 In the former species this is to be seen simply as a swelling beneath 

 the skin, in the latter it is flap-like, with a free margin behind and 

 at the sides. It springs from the anterior extremities of the fronto- 

 parietal bones, which are swollen and markedty pitted at this point. 

 The swelling itself is composed of dense fibrous tissue, and is 

 connected posteriorly to the skin above it by fibrous bands ; in the 

 case of R. pileata it is closely adherent to the skin all round the free 

 margin of the flap. 



The following key, based on adult male characters, will serve 

 to distinguish the various forms : — * 



Head not enlarged, no tooth-like projections 



in the lower jaw R. dor ice Blgr. 



Head enlarged, lower jaw with tooth-like 



projections — _. 



No postorbital swelling R. kohchanga, nov. 



Postorbital swelling rounded, reaching to 

 level of anterior border of tympanum, 

 heels overlapping R. macrognathus macrognathus Blgr. 



Postorbital swelling elongate, reaching to 

 level of posterior border of tympanum, 

 heels not overlapping R. macrognathus dabana, nov. 



Postorbital swelling flap-like with a free edge R. pileata Blgr. 



* The allied R. plicatella Stoliczka, has also an occipital knob, but 

 with its characteristic dorsal folds of skin and shorter web to the toes is 

 quite distinct from the forms discussed here. 



JOURN. NAT. HIST. SOC. SIAM. 



