DEVELOPMENT OF THE SKULL IN TUE BATRACHIA. 149 



The hyo-branchial plate (fig. 8, h.h.hr.), witli its outgrowths, falls short of the type 

 in having no hypo-hyal lobes, and in the small size of the front lateral lobes ; the 

 thyro-hyals it.hj.) are rather slender, and only diverge gently. 



The investing bones are very similar to those of the type, but modified so as to fit 

 to a more outspread cranium. The roof-bones {/.p.) are strong, very wide, and as in 

 most of this Family are veiy scant in front, especially near the mid-line. The nasals 

 (??.) make no pretence of covering the skull in their region, for they are very narrow 

 crescentic shells of bone. The premaxillaries {px.) are, perhaps, the largest in the 

 Order, bounding, as they do, so wide a nasal fore wall. 



There are no septo-maxillaries ; the maxillai'ies {mx.), the quadrato-jugals {q-j.), and 

 the squamosals {sq.) are all strong, well developed, and normal. So also is the para- 

 sphenoid (fig. 6, pa.s.) ; it is very sharp, both behind and befoi'e. The vomers {v.) stretch 

 far across the nasal floor, but fail to meet ; they have the usual four-snagged form ; 

 the large thick tooth-bearing lobes are arcuate, and their concave margin is behind. 



The relation of this type of skull to the others in this Family is evident ; this is the 

 fullest expression of the Polypedatine type, and thus the greatest divergence from 

 the ybi'm of the Ranine skull is obtained. We have to remark upon — 



1. The short auditory and occipital region, the wide orbital, and the wide and long 

 nasal region. 



2. The fusion of the bones of the hind skull. 



3. Unusual solidity and strength of the pedicle. 



4. The inter-stapedial ossifying as part of the shaft, appai-ently without absolute 

 segmentation of the cartilage. 



5. The confluence a,bove of the supra-stapedial and stylo-hyal bands. 



6. The feebly expressed cartilages of the hypo-branchial plate. 



7. No septo-maxillaries. 



8. A distinct superorbital eave. 



9. The grafting of the premaxillary on the " 1st upper labial." 

 All these modifications are gentle and non-essential. 



Third genus. Ixalus. 

 38. Ixalus variabilis. — Adult female ; 1 inch I line long. Ceylon. 



This skull differs very little indeed from that of Polypedates maculatus; it would 

 differ still less from that of a young individual of that species of its own size.* 



It is a short skull, and the length bears to the breadth the proportion of 7 to 8 ; it 

 is therefore a trifle narrower than that of Polypedates maculatus. The outline is 

 extremely regular, and is half an ellipse, whose long diameter may be put as 13 and 



* Di'. GCnther Ls now inclined to consiilcr tlii.s species as tlio young of roli/pedates mactthtttis ; but the 

 well developed supi-a-stapedial band, and the absence of an inter-stapedial and of secondary fontanelles, 

 makes this doubtful. 



