SKELETON OP THE ANUROUS BATRACHIANS. 477 



In early tadpoles, whicli aloue are now under consideration, 

 the posterior margin o£ the hypobrauchial cartilage is but 

 slightly indented by the laryngeal sinns, for the sides of this are 

 bounded mainly by the spicula of the fourth branchial bar. This 

 is absolutely the case in Leptohrachium (fig. 4, Is.), but the 

 generalization does not hold good for the Discoglossidee, and is 

 •only partially applicable to such genera as Pseudis (fig. 5) and 

 Hhaco^phorus. In Oxyglossus, where there are no spicula, the 

 laryngeal sinus is merely a notch at the back of the hypo- 

 branchial plate (fig. 6, Is.). The distinctness of the fourth spicula 

 from the hypobranchial plates is most clear in Leptoibraohium 

 (fig. 4, 5J5.-^), in which these cartilages are very large; they are 

 but feebly dift'erentiated in Pseudis (fig. 5). It is of some 

 interest to note that the first eeratobranchial is fused with the 

 cartilage of the hypobranchial plate in all the forms examined 

 except Alytes, Pomhinator * (fig. 1, ch}), and Discoglossus (in 

 which genera the union is effected by connective tissue), because 

 in Pelodytes the basal portion of the bar persists as the processus 

 posterolateralis of the adult hyoid (12. p. 590), whereas in Alytes 

 the whole of the eeratobranchial skeleton is ultimately resorbed. 



Microhyla, Xenopus, and Pipa are too exceptional to come 

 within the scope of the foregoing generalizations, and these 

 genera are, therefore, treated of only in the succeeding " Special 

 Part." 



The results of the present investigation cannot be said to 

 have solved the problem of the morphological value of the 

 hyobranchial copulse of the Anuran larva. The most natural 

 inferences to be drawn from the arrangement of the parts of 

 the hyobranchial skeleton of the Discoglossidse are that the 

 anterior copula is the equivalent of the basihyal of the fish, and 

 that the posterior copula is a basibranchial. Bat in such forms 

 as Pana and Pelohates the single copula present is situated 

 quite anteriorly to the branchial part of the skeleton ; and 

 although this fact does not prevent it still being regirded as a 

 basibranchial (seeing that in Notidanus the basibranchial is 

 situated anteriorly to the hypobranchial elements of the arch), 



* This relation in BovAinator has already been pointed out by Gotte (5. 

 p. 679). 



