215 



THE FROGS ALLIED TO RANA DORI/E. 



By Malcolm A. Smith, f.z.s. 



With plate 9. 



The frogs clustered round Rana dorkv Boulenger, form a 

 t small and compact group, easily separated from all other species 

 affiliated to them, but not so readily distinguished among themselves. 

 The reason for this difficulty lies in the fact that it is only by means 

 of the unusual development which occurs in the heads of the adult 

 males that separation is possible. In bodily configuration, in the 

 position of the vomerine teeth, in the character of the skin, the 

 extent of webbing to the toes, and in colouration, they closely resem- 

 ble each other, so nearly, that where females or juveniles are con- 

 cerned, it is practically impossible to distinguish between them. 

 Clearly they are all derived from a common ancestor, and they might 

 still, perhaps, be regarded as racial forms of one species. The male 

 characters, however, are now so distinct and constant, and the range 

 of each form appears to be so well defined,* without intermediate ones 

 occurring that, with one exception, it seems advisable to accord them 

 specific rank. In several localities, moreover, two forms are to be 

 found together. Further information concerning the phylogenetic 

 relationships of this group, may be forthcoming when all its tadpoles 

 are known. I have so far been able to obtain only two of them. In 

 all essential characters these two do not differ from each other. 



The range of these frogs is- throughout Siam and the regions 

 immediately bordering thereon. They are hill dwellers, inhabiting 

 the mountain streams at all levels up to 1000 metres; and where 

 found they are usually abundant. Excepting R. dorice, I have had 

 the opportunity of seeing them all in their native haunts. 



With the large amount of material now in my possession it is 

 possible to review this group in considerable detail. I recognize five 

 forms. Three of these, R. dorice, R. macrognathus and R. pileata 

 are already known. Two more are now added, R. kohchangce and a 

 new race of R. macrognathus. 



* Except in the N. and N. E. where extensive collections have not 

 yet been made. 



VOL. IV, NO. 4, 1922. 



