ii4 Records of the Indian Museum. [Vol. XXIV, 



In working through the large collection of Pontoniinae in the 

 Indian Museum I have derived much assistance from the memoir 

 which Borradaile has recently published ' ; his full lists of references 

 to the species have been most useful to me. On a large number 

 of taxonomic questions, however, I have formed conclusions which 

 differ very widely from those which he has expressed, particularly 

 in regard to the generic subdivision of the group. The latter 

 question, as Borradaile has pointed out, is one of great difficulty. 

 In the course of my work I have repeatedly been struck by the 

 very homogeneous nature of the subfamily as a whole, and it is 

 to this fact that we must turn for an explanation of the ap- 

 parently trivial characters on which many of the genera have 

 been founded. 



The characters used for the generic subdivision of the Ponto- 

 niinae contrast very strongly with those employed for the same 

 purpose in certain other families and subfamilies of Caridea. In 

 the Hippolytidae, for example, we find that the genera can be 

 separated by trenchant morphological characters based for the most 

 part on the branchial formula, on the structure of the mandible 

 and on the carpal segmentation of the second peraeopods. We 

 are thus able, in this family, to devise a scheme of classification 

 which should satisfy even the most earnest seeker after phylo- 

 genetic truth ; we have confidence that our genera form natural 

 groups and that they can be arranged in a manner which will de- 

 monstrate their true affinities. 



The Pontoniinae present a far more difficult problem. We 

 search almost in vain for important morphological features which 

 will serve to separate the large assemblage of species into natural 

 groups. We are obliged to define our genera on characters of a 

 much inferior order of magnitude and we are often far from certain 

 that they are phylogenetically valid. 



This radical difference between two not distantly related groups 

 of Caridea is perhaps to be explained by supposing that the Pon- 

 toniinae have succeeded in evolving a structural type that can be 

 adapted without any deep-seated modifications to all needful 

 kinds of environment ; whereas the Hippolytidae, with a less 

 useful stock-pattern, must needs undergo drastic change, some- 

 times assuming the most bizarre forms, in order to equip themselves 

 for particular conditions of life. In this connection it is to be 

 remarked that the Pontoniinae have proved themselves far superior 

 to the Hippolytidae in their ability to accommodate themselves to 

 unusual surroundings. 



In subdividing such a homogeneous group as the Pontoniinae 

 it is, I believe, of first importance that the genera should be est- 

 ablished on a broad basis and that the characters used in separat- 

 ing them should so far as possible be unequivocal. That the classifi- 

 cation of the family has hitherto been greatly lacking in this respect 

 is clear from a study of the literature. As evidence of the confu- 



1 Borradaile, Trans. Linn. Soc. (2) Zool. XVII, p. 323 (1917). 



