DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 53 



into it, we see tlie postorbital process wliich is tlie curved blade ; together, they are 

 half as long as tlie whole skull (see fig. 8). Also the angle at which the stem runs 

 down over the massive quadrate and its condyle is very remarkable (compare figs. 3 

 and 8, sq.), for the axis of the postorbital process is almost coincident with it, and 

 between the stem and the supra-temporal plate the space is only half a right angle. 



The roof and floor have been wrought over the inner skull, above and below, so as to 

 half liide it ; thus the parasphenoid and the frorito-parietals are bony troughs or 

 hollow sphnts. The latter {f.p.) are quite distinct, right and left, very long, narrow, 

 naiTowesb in the middle, not very wide in the temporal region, where their edge is 

 emai'gmate, curving with the canal below ; whilst in front they are overlapped by 

 the nasals [n.) and hide the girdle-bone : outside they do not hide the superorbital 

 cartilages (s.ob). The nasals form a pair of large wings and are highly arched and 

 strong (fig. 8) ; the outer part is an elegant facial hook, binding on the upper edge of 

 the maxillary ; the two bones meet all along, forming a nasal suture. 



The parasphenoid (figs. 7 and 8, j:)o..s') is a very long trough of bone of the usual 

 shape, with well-formed basi-temporal wings that are trilobate. 



The hyo-branchial plate (fig. 9) is quite normal in form ; there is a slight fissure in 

 the substance of the " hypo-hyal " lobe {h.hy.) ; a division of the hyoid cornua into an 

 oviter and an inner tape not uncommon in. the Batrachia : the outer is a remnant of the 

 pectinate inter-branchial cartilage such as we see in the Chima3roids and then- kindi-ed. 



Compared with the type, Rana Kuhli shows the following divergences of character : — 



1. No septo-maxillaries. 



2. Dentary with a very large tooth-shaped process. 



3. ArticiUation of pre-maxillaries and maxiUaries very wide and high, to admit of 

 the process of lower jaw. 



4. Stylo-hyal confluent, above. 



5. Extra-stapediad a very large cordate disk, peltate, and without supra-stapediai. 



6. Superorbital cartilaginous, and very distinct. 



7. Eustachian openings very small. 



I have already mentioned the peculiar fonn of the skull, and of certain individual 

 bones, but the above are the most important morphological variations. This skull \h 

 altogether very instructive and suggestive ; R. Kuhli is certainly a "borderer," and I 

 suspect it has retamed some very archaic characters that have been more or altogether 

 obhterated in the other species of its genus and its territory. 



c. North American (" Nearctic ") species. 



2 (continued).* Rana pipiens, Hael. — {R. cateshiana, Shaw; R. mugiens, Merr.). 



This specimen was considerably larger than those of the Indian Bull-frogs just 

 described. 



* See p. 22 where the larva of this species is described. 



