THE SKELETON 27 



other two processes, removed entire. The quadrate (o.qu.) forms the 

 direct lateral continuation of the basal process and points almost at 

 right angles to the skull axis in an obliquely downward direction. 

 It articulates directly with the lower jaw and always ossifies to a 

 greater or lesser extent, being in fact the only portion of the suspen- 

 sorium to do so normally. Th.Qprocessus pterygoideus^ or 'cartilaginous 

 pterygoid' (c.pt.), arises from an independent chondrification in the 

 2,^ mm. larva (Stadtmuller) but is continuous with the palato-quad- 

 rate in the adult, from which it protrudes antero-laterally towards the 

 posterior end of the maxilla, pointing somewhat obliquely down- 

 wards. It is only a narrow rod of cartilage and lies in a groove in the 

 osseus pterygoid (which belongs to the investing bones of the skull) 

 and usually protrudes a short distance anterior to it. 



The suspensorium is attached to the maxilla by two ligaments, 

 the jugal ligaments^ namely lig. quadrato-maxillaris externum and the 

 lig. quadrato-maxillaris internum^ which pass laterally and mesially of 

 the M. levator mandibulae respectively. 



3. The Investing Bones. 



In contrast with the slow and tardy ossification of the replacing 

 bones the investing bones arise very early, and are already well 

 formed at birth, so that it is advisable to treat any larva with either 

 a decalcifying fluid or an acid fixative before attempting to section 

 it. Nevertheless they always remain thin and leaf-like. The follow- 

 ing bones are present: on the dorsal side, pre-maxilla, maxilla^ nasal^ 

 frontal^ pre-frontal, parietal^ squamosal — all are paired. On the ventral 

 side there is an unpaired median parasphenoid and paired pre-vomers 

 and pterygoids^ while both the pre-maxillae and maxillae have palatine 

 processes. According to Stadtmuller a quadrato-jugal occurs, appear- 

 ing first in a larva of 27 mm., but it always remains small and, in 

 the adult, fuses homocontinuously with the palato-quadrate so as to 

 be indistinguishable. 



The pre-maxillae (o.p-m.) are paired in the Salamander and form 

 the skeleton of the snout. They are sometimes called intermaxillaries 

 (Funk, Bolkay). Three regions are distinguishable in each bone 

 which, according to Stadtmuller, arise as three distinct ossifications. 

 These are : {a) the pars prenasalis (or dorsalis) which ascends over the 

 dorsal side of the nasal capsule and ends in a sharp slender process 

 which to some extent overlaps the nasal and frontal, (b) The pars 

 den talis forms the anterior border of the upper jaw and bears teeth — 

 it is in fact formed by the fusion of tooth sockets. It is joined to 

 the pars prenasalis dorsally and to the pars palatina postero-mesially. 



