122 THE ANATOMY OF HYLA C.ERULEA WHITE. 



the squamosal (fig. I, sq.a.) lies along the outer side of the 

 posterior limb of the pterygoid (fig. 1, 2>^.a.) and also fits 

 over the dorsal edge of this ramus by means of a groove 

 on its ventral surface. The proximal portion is flattened, 

 but the distal region is rod-like and curved, with the con- 

 cavity facing outwards. The shorter arm of the transverse 

 bar (fig. I, sq.c.) is directed postero-dorsally and the longer 

 (fig. I, sq.b.) antero-ventrally. Both the anterior and 

 posterior rami of the pterygoid (fig. II, ^J^6. ; pt.a.) are 

 curved, in the former the concavity being internal, but 

 external in the latter. The inner ramus (fig. II, ptx.) 

 runs inwards and slightly posteriorly towards the otic 

 region. On its postero- dorsal surface it is strongly grooved. 



The Skull of Hyla aurea. 



The skull of Hyla aurea is more pointed than that of 

 H. ccerulea, and its breadth is approximately equal to the 

 length, hence proportionately it is less than in H. ccerulea. 

 The anterior fontanelle is completely roofed over by the 

 fronto-parietals meeting medianly, this condition differing 

 from that of H. ccerulea in which the fronto-parietals do 

 not meet along the major portion of their length leaving 

 the fontanelle open. The chondrocranium between the 

 sphenethmoid and occipito-otic region is more extensive 

 than in H. ccerulea. 



Our thanks are due to Dr. T. H. Johnston for per- 

 mission to use the laboratory and material of the Depart- 

 ment of Biology. 



BIBLIOGRAPHY. 



1. Gadow, H. Amphibia, Cambridge Natural Histor}', 1909. 



2. Marshall, A. M. "The Frog" 1912. 



3. Parker, W. K. " On the structure and development of the skull 

 in the Bitrachia " pt. II. Phil. Trans., 1876, pp. 601-669. 



