56 "ME. W. G. EIDEWOOD ON THE HTOBIIANCHIAI, 



are not of the same standard of excellence as the rest of tlie 

 work. 



Such, briefly stated, is the extent of our present knowledge on 

 the subject. Witli the various conflicting views and contra- 

 dictory statements before me, I set myself to ascertain to what 

 extent, if at all, the hyobranchial skeleton enters into the form- 

 ation of tlie laryngeal box in the Aglossa ; whether the lateral 

 laryngeal ossifications of Xenopus are really the thyrohyals, and 

 whether the ossifications in the floor of the larynx of Pipa are 

 homologous with these, A further object of the investigation 

 was the determination of the morphological value of the great 

 wings of the hyobranchial skeleton in Xenopus and Pipa ; the 

 experimental verification of the assumed absence of the hyoidean 

 cornua in Pipa ; and an inquiry into the functional value of the 

 great arytenoid rods which lie in the interior of the larynx in 

 the male of this genus. The results of the investigation are 

 arranged in the following order : — First, a comparative treatment 

 of the adult hyobranchial skeleton of Xenopus and Fipa, in- 

 cluding a detailed account of the laryngeal skeleton of both 

 sexes ; then a description of the laryngeal muscles of the two 

 genera ; the details of the development of the hyobranchial and 

 laryngeal skeleton ; and, in conclusion, a few observations on the 

 bearing of the facts on the problem of the afiinities of Xenopus 

 and Pipa to one another and to the tongued Anura. 



Before proceeding farther, I take the opportunity of expressing 

 my grateful acknowledgments to Sir "William Flower, K.C.B., 

 for placing in my way every facility for the execution of this 

 research. In addition to the adults of Xenopus and Pipa, which 

 by the kindness of Sir William Flower I was permitted to 

 examine at the Natural History Museum, I have received 

 numerous specimens, both larval and adult, from Prof. G. B. 

 Howes, of the Eoyal College of Science, Mr. F. E. Beddard, 

 F.E.S., and Mr. G. A, Boulenger, F.E.S. ; and to them my thanks 

 are hereby gratefully tendered. 



Htojbeajtchial Skeleton of Xenopus Icevis, female. 



In describing the hyobranchial and laryngeal skeleton of the 

 Aglossa it is advisable to commence with that of the female 

 Xenopus, firstly, because in Xenopus this portion of the skeleton 

 is less aberrant than in Pipa, and, secondly, because the modifi- 

 cation is less in the female than in the male. By choosing the 



