523 



On two New Species of Philodina. 



By David Bryce. 



{Read June Idfh, 1903.) 



Plate 27. 



Although a few of the species belonging to the genus Philodina 

 can be readily identified by means of their pronounced and obvious 

 peculiarities of structure, the majority, forming what may be 

 called the central group, agree somewhat closely in all the more 

 important or salient details, and can only be recognised with 

 any approach to certainty by attention to points which, to the 

 uninitiated, may seem to be exceedingly trivial. In the closely 

 related genus Callidiiia, with its much greater array of species, 

 the difficulty of identification is greatly lessened by its wdde 

 range of variation, and one is able to rely with confidence upon 

 characters afforded by the proportions of the corona, by the 

 form of the upper lip, by the number of teeth, by the treatment 

 of the food, and by the structure of the various parts of the 

 foot. 



In the central group of the genus Philodina there is compara- 

 tively little variation in any of these details, with the exception 

 of those processes upon the penuhimate^foot segment known as 

 the spurs. In the form, length, distance apart, and direction of 

 these processes there is considerable, although perhaps not very 

 conspicuous, variation. So far as I have been able to judge, the 

 individual variation, or that which obtains among the individuals 

 of one species, is extremely slight, whilst the specific variation {i.e. 

 as between the different species) is sufficiently characteristic and 

 remarkably constant. I have come therefore to rely mainly upon 



