SKELETOlSr OP THE AlfUROUS BATEACHIANS. 481 



In spite of the extreme minuteness of the whole hyobranchial 

 skeleton, such features as the ligamentous band in the hyoglossal 

 sinus and the space at the side of the copula can be easily made 

 out by ordinary dissection. 



ENaXSTOMATIDiE. 



The tadpoles examined were collected in Siam and presented 

 to the Natural History Museum, London, by Mr. Stanley Elower,. 

 and were reported by him to be the offspring of Microhyla 

 ornata. They bear a remarkable resemblance to the larvae of 

 Xenopus of the Cape, in shape, general transparency, and the 

 silvery appearance of the abdomen. 



The hyobranchial skeleton is most singular (fig. 3). The 

 hypobranchial plates are fused across the median line, and have 

 a thickened anterior margin which is fused with the hind end of 

 the copula. The place where the pars reuniens normally occurs 

 is occupied by a transverse bar of cartilage, fused at its ex- 

 tremities with the ceratohyals. The postero-internal parts of 

 the ceratohyals are free, and overlap the anterior edge of the 

 hypobranchial plate. The hyoglossal sinus is shallow, and the 

 transverse ligamentous band is very distinct. The ceratobranchial 

 skeleton has the form of a pair of great pouches perforated at 

 the bottom by three slits, and in this respect, also, the tadpoles 

 under consideration resemble Xenoptis. The laryngeal sinus is 

 narrow and deep, but owing to the fourth ceratobranchials being 

 in contact with one another behind it, as in Xenopus, the larynx 

 itself is situated very far back. 



It would be interesting to ascertain what are the conditions 

 of life which, have evidently been instrumental in bringing 

 about these external and these skeletal resemblances between 

 two such remotely allied genera as Microhyla and Xenopus. 

 That the two results have been arrived at indej)endently is, I 

 think, beyond question, for although the resemblances are so 

 striking at first glance, the similarity does not extend into the 

 smaller structural details. 



Ctstignathid^. 



Of the four genera examined, two {GMroleptes and Telma- 

 tobius) resemble one another so exactly in the structure of their 

 larval hyobranchial skeleton that one of them may be dismissed 

 at once. Fseudis di£fers from these in several respects, notably 



