180 MR. W. K. PARKER ON THE STRUCTURE AND 



The lateral lobes are well developed, the foremost are stalked obovate leaves, the liinder 

 pair are ligulate; altogether, this is one of the most remarkable and elegant hyo-bmnchial 

 structures to be seen in the Order. 



The investing bones are full of interest : the fronto-parietals {/.p.) are oblong, 

 rounded, however, and scarcely dilated behind, and having a transverse dentated front 

 margin ; they barely overlap the endocranium (fig. 7). Contrary to rule, they cover in 

 the fontanelle {under /.p.), as in the larger " Polypedatidse." 



Over the large fore skull the nasals {ii.) are nearly as large as the fronto-parietals; 

 they only touch the edges of the septum nasi (*•.«.) and do not meet each other ; they 

 are crescentic shells, with a facial " handle." 



The premaxillaries (pa?.) are narrow, and so is the palatine portion of the maxillaries 

 {rax.), but the facial part, although extremely thin, is high : there are no septo- 

 maxillaries. 



The quadrato-jugals {q.j.) ai-e sharp and curved; they are well grafted on to the 

 quadrate ; the squamosals {sq.) are well developed, the supratemporal part is lozenge- 

 shaped, and sends outwards and forwards a long narrow poatorbital process. The 

 parasphenoid {p>a.s) is not two-fifths the length of the skull, it is a very elegant 

 dagger, with backwardly bent narrow processes for the guard, and a short triangular 

 handle. The vomers (v.) are long and slender; the tooth-hillocks are sub-crescentic, 

 the pre- and post-narial spikes are long, and the fore part a short pointed process. 

 This skull is a very exquisite structure, differing from that of the " pattern " rather in 

 a certain dehcacy of the parts and the hght airy character of the Avhole, than in any- 

 thing essential ; some things may especially be noticed :— 



1. There is only one fontanelle. 



2. The bones of the hind skull are confluent on the same side. 



3. There is a cartilaginous process, and also a distinct cartilage, in the fore angle of 

 the orbit, above. 



4. There is a short prenasal rostrum. 



5. There are no septo-maxillaries. 



6. The girdle-bone has its sides partly formed of ossified membrane. 



7. There is a short hinder projection from the basal plate, and some endostosis there ; 

 and the whole of that apparatus is very remarkable in the shortness of the plate, the 

 depth of the front notch, and the great length of the arcuate thyro-hyals ; but these 

 things, and many more, which the figures will show, are almost undefinable modifica- 

 tions of the typical form, and this Tree-frog is just such a refinement, so to speak, of 

 the typical Fi'Og, as that is of the Common Toad. 



50. Hyla 1 sp. — Tadpole, 1 inch long ; hind legs, 5 lines. Kio Janeiro. 



These, and the skulls of more advanced larva) o^ Nototrema mnrstipiatum (Plate 30, 

 figs. 8, 9, and 10-13), show that the modification of the larval Batrachian chondro- 



