365 



ON THREE NEW SPECIES OF CALLIDINA. 



By David Bryce. 



{Bead March 26th, 1912.) 



Plate 12. 



The description of three new species of Bdelloid Rotifera affords 

 a,n opportunity of recommending attention to the form of the 

 Upper Lip as one of the most valuable characters which go to 

 make up the individuality of species of the Philodinidae. The 

 earliest mention of this structure which I have found is by 

 Milne (18), who early in 1886 referred to it as the "brow," and 

 very briefly pointed out its different forms in three species then 

 described. Later in the same year Zelinka (20) named it the 

 Upper Lip (" Oberlippe "), and made use of it in his descriptions 

 of two new species; and again, in 1891 (29), gave "the form of 

 the corona and of the upper lip " as the third of eleven characters 

 which should be ascertained as far as circumstances permit and 

 included in the description of any species of the genus Callidina. 



The upper lip is not possessed by all the Bdelloida, but only by 

 those which constitute the family of the Philodinidae. Although 

 perhaps, strictly speaking, it is not actually a part of the corona, 

 jet it is only visible when the wheel organ is displayed, and it is 

 withdrawn with it within the mouth when the animal resumes 

 its normal or creeping position. That being the case, it is con- 

 venient to look upon it as a subsidiary part of the corona, of 

 which in many cases it has become the dominant characteristic 

 (from the point of view of the student). 



When the ciliated discs on their pedicels have been pushed 

 forth from the widely opened mouth, the upper lip comes to be 

 visible in direct dorsal view as an unciliated surface of the head 

 in front of the reverted rostrum, merging gradually at either side 

 into the "collar," the wider part immediately succeeding the 

 lateral bases of the pedicels. 



In a few of the tube-dwelling species Hahrotrocha longiceps, 

 H. Leitgehii, etc. the upper lip has been considerably enlarged 

 so as to become long in proportion to the breadth of the head, 



