474 DE. W. G. EIDEWOOD ON" THE LAETAL HTOBEAlSrCHIAIi 



On the Larval Hyobranchial Skeleton of tlie Anurous Batradiians^ 

 with Special Eeference to the Axial Parts. By W. Gr. 

 EiDEWOOD, D.Sc, r.L.S., F.Z.S., Lecturer on Biology at 

 St. Mary's Hospital Medical School, London. 



[Eead 20th January, 1898.] 

 (Plate 31.) 



Ikteoduction. 



The observations recorded in the following pages were made with 

 the especial object of ascertaining whether the peculiarities of 

 the larval hyobranchial skeleton of Alytes are common to all the 

 genera of the family Discoglossidse, and whether they occur in 

 any genera not belonging to this family. The peculiarities in 

 question consist in the presence of an anterior copula, and the 

 complete separation of the hypobranchial plates by the posterior 

 copula, which thus extends back to the laryngeal sinus, as already 

 fully described in a communication recently presented to the 

 Zoological Society, and appearing shortly in the ' Proceedings.' 



Tadpoles of twenty-one species were examined, belonging to 

 nineteen genera; and for all of the specimens I am indebted 

 to Mr. Gr. A. Boulenger, F.E.S., whom I haA^e always found most 

 ready and anxious to encourage morphological enquiries of this 

 kind, and to whom my thanks are hereby gratefully tendered. 

 Considering how few of the species of Anura are known in their 

 larval stages, the following list will be admitted to be very 

 complete and representative. 



The three numbers of the formula appended to each name 

 stand respectively for the distance in millimetres from the snout 

 to the root of the tail, the length of the tail, and the length of 

 the hind limb. No measurement is given of the fore limb? 

 because, in order to make the comparison between the different 

 species as perfect as possible, the tadpoles were all selected at 

 that stage in which the larval hyobranchial skeleton is most com- 

 plete and most characteristic. This stage is recognized externally 

 by the small size of the hind limbs, and by the fact that the fore 

 limbs are not yet extruded through the atrial wall. 



