416 



IIAKHIS HAWTHORNE WILDER ON 



converge at the posterior end. There is necessarily a slight depression between them, 

 but anything as marked as the depression described by Wiedersheim and likened to a 

 "sella turcica," I have failed to find. Probably this outline wovild be much more noticeable 

 in cross sections, which were studied extensively by this author, and in a young animal it 

 is likely that it would be proportionally more marked. The parabasal normally comes into 

 contact with ten bones, eight upon the dorsal surface and two upon the ventral. Doi'sally 

 there are found in order, the two frontals, and the two parietals, by their uncinate and 

 orbito-sphenoid processes respectively ; the two pro-otics, and tlic two exoccipitals, the 

 latter almost anchylosed with it in old adults. Upon the ventral side are the two vomers. 

 The palato-pterygoids and the opisthotics come very near the parabasal, but form no defi- 

 nite area of contact. 



The ujjper jaw. — Under this term may be included all the dentigerous bones of the 

 skull proper, as the teeth of all these oppose those upon the mandible. In this groiip 

 both of the typical arches are represented, the maxillary and the palato-quadrate, or the 

 "inner" and "outer arches" of W. K. Parker, the former by the premaxillaries and the 

 latter by the vomers and palato-pterygoids. Each of these arches bears a row of teeth, 

 and, when the mouth is closed, the single row on the mandible is received between the two 

 upper rows. The internal or palatine row is longer than the external or maxillary. 



1. THE MAXILLARY AHC'iL Tliis arch is represented in most Urodeles by both pre- 

 maxillaries and maxillaries, the latter extensive and ending in long, backwai'd projecting 

 processes which, in the recent state, are attached by strong ligaments to the quadrates, 

 thus making the arch a complete one. In Necturus it suffers much reduction and is 

 represented by the premaxillaries alone. The maxillary fails completely, and no rudi- 

 ment of it seems to be present at any developmental stage. Hyrtl describes a dried 



specimen with a small but tooth-bearing maxil- 

 lary upon one side. Neither Huxley nor Wie- 

 dersheim could find a trace of it, and in an 

 examination of more than fifty skulls I have 

 never seen it. The specimen described by 

 Hyrtl must have been either an abnormal case 

 or one of mistaken identity. 



a. PremaxiUary. — This bone consists of 



a slightly curved alveolar portion, to the inner 



end of which an ascending process is added at 



nearly a right angle. The alveolar portion is 



placed in an antero-lateral position, ventral to the large nasal capsule, which lies obliquely 



across it and forms the anterior part of the outer margin of the skull. The ascending 



Two views of ri^lit preiaaxillary 



X 



