DEVELOPMENT OF THE SKULL IN TUE BATRACHIA. -liJ 



The thyro-hyals are long and straddling, with much cartilage at the end, and on the 

 left side there is a round nucleus of cartilage {t.h>j'.) outside the hone, proximally. 

 Just behind the front lobes a band of endostosis runs across the plate — a faint attempt 

 at the formation of a bony " 1st basi-branchial." 



The investing bones are coarse and strong but limited in their superficial extension. 



The fronto-parietals (fig. Ijf.p.) are roughly radiated, grooved externally, and pitted 

 in the hind part, where they very imperfectly cover the hind skull. 



Tlieir oblique temporal groove is inside the combined ai-ches of the anterior and 

 posterior canals (fig. 1, au.), and their ragged expansions are anchylosed to the prootics 

 within. They are mere thick bars on each side of the naked fontanelle, and overlap 

 the girdle-1)one {eth.) in front. The nasals (>;.) are large, long-handled below, and do 

 not quite meet over the septum-nasi. 



The premaxillaries (px.) are gently arcuate, of great extent, and have well developed 

 nasal and palatine regions. 



The maxillaries {mx.) are also well developed, with a considerable palatine edge that 

 broadens behind before it gives off its jugal process ; there is between these bones a 

 small angular septo-maxiUary {s.mx.). The quadrato-jugal [q.j.) is a short curved 

 spike, partly confluent with the quadrate (f/.). 



The squamosal {sq.) has a rough, short upper, and a gently expanding lower, limb. 

 The parasphenoid (pa.s.) has all its processes weU developed, it is quite Bufonine, 

 narrowing rapidly in front, and with very extended lateral processes that run to a 

 point ; the handle is large and notched behind ; and the opposite process, under the bone 

 at its basi-temporal part, is an extended oblique toothed ridge. 



The vomers (fig. 2, v.) are small, with a prenarial hook, a hooked fore part, and a 

 notched hinder process. 



In this skull the Bufonine characters are arrested and modified : this is especitdly 

 seen in the deficiency of the roof bones, in the continuousness of the palato-suspensorial 

 cartilages, and in the perfect freedom of the pedicles. It, thei-efore, is not 'so 

 different from a Frog's skull as that of its congeners. 



From the " norma " it differs in — 



1. The o-eneral strength and coarseness of its structure. 



2. Tliere are no secondary fontanelles. 



3. Tlie main fontanelle is uncovered. 



4. There are no dentigerous bones. 



5. There is a superficial (" parosteal '') palatine. 



G. The pterygoid is most developed below, and not above, 



7. The mandible is unusually cartilaginous. 



8. There is no inter-stapedial ; and the supra-stapedial and stylo-hyal are confluent 

 above. 



