DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 153 



distinct from the continental form — //. mcdabarica. I have just described that species, 

 and when this has been compared with it then all doubt will vanish as to their 

 distinctness ; both kinds attain the length of three inched!, or thereabouts ; my speci- 

 mens of//, malciharica are all young, and only a quarter the length of the adult; yet 

 the ossification of their skull is much more perfect than in the adult of the Ceylonese 

 kind ; there are also other differences, as we shall see. 



This is a long skull (Plate 29, figs. 1, 2), for the length is equal to the breadth ; it is 

 extremely like that of Polypedates chloronotiis (Plate 2G, figs. 1, 2), but is not so long ; 

 in that species the length is about a twelfth greater than the breadth ; and that kind 

 has its ossifications intenser, and has no evident superorbital "eave." 



Although belonging to the narrow-skulled group of this Family, the cranium proper 

 is in reality very broad, half as broad again as in an average species of Rana, and 

 therefore settling this as a character of the Oriental flat-toed Froo-s. 



They are, indeed, a broad-muzzled, flat-skulled race, but when flattened most their 

 skull is very Ranine as compared with that of a true Hyla. 



The occipital condyles (Plate 29, figs. 1, 2, oc.c.) are large, posterior, and separated 

 by a crescentic emargination half their breadth. Measured along the axis, the occipital 

 region is half, and the nasal two-thirds, the extent of the orbital, which is very large. 

 The "tegmen cranii" covers two-thirds of the skull, and grows in well from the 

 sides, so that the larger cordiform fontanelle is small, and the secondary spaces very 

 minute. 



The parotic wings stand out well, and the canals {a.s.c, h.s.c, p.s.c.) are prominent. 

 The ossification, right and left, is only equal that of the type, and the four normal 

 centres {pr.o., e.o.) are separated by extensive tracts of cartilage. Above, the prootic 

 stretches out in front so as to underlie the squamosal a little. Below, the floor of the 

 vestibule (cm.) is unossified, for the ex-occipital.s, which flank the posterior canal above, 

 do not reach to the fenestra ovalis below. In front, the prootics just reach the optic 

 fenestras (II-)- Of the remainder of the long orbital region the hinder half is unos- 

 sified ; the rest, or the region of the "girdle," is partly ossified, and partly caZci^ec?, 

 the latter tract marking out the usual extent of the bone, which however is only 

 fully developed in front into an irregular (J -shaped bone, thick and rugged, but whose 

 halves do not meet above (fig. 1, etJi.). In front, this imperfect girdle scarcely covers 

 the proper ethmoidal territory, and the whole nasal region, and likewise the extensive 

 superorbital crescents {s.oh.), are unossified. Leaving these out, the form of the orbital 

 region of tlic skull is ()l)long, modified by a slight bulging, and a gentle increase of 

 breadtli, forwards. 



The nasal territory (al.H.) is large and four-square, with the roof .spreading wider 

 than the floor ; the septum (s.n.) is thick, and both above and below we can see clearly 

 how much has been added to the original " trabecular horns " by the solid inter- 

 trabecular wedge (or wcdl), and how much by the large shells of cartilage that form 

 the roof. Tlieir division also, into the floor (with its angles that bury themselves 



MDCCCLXXXI. X 



