68 The Ottawa Naturalist. [October 



temporal fossa is restricted in its upper half-length, and the ascending 

 process of the jugal is relegated to a position on the inner side of the 

 pocket well-removed from the outer surface of the skull. 



Prefrontal. Is in contact with the frontal, nasal and lachrymal, 

 and forms the supero-anterior curve of the orbital rim. It overlaps the 

 nasal to a considerable extent, and slightly overlaps the lachrymal. Its 

 inner surface in advance of the orbital rim is excavated, leaving the 

 bone thin. 



Nasal. This bone is long and narrow, very slender in its 

 anterior half-length, and relatively broad behind. It is in contact with 

 the frontal, prefrontal, lachrymal, maxillary and premaxillary. 

 Anteriorly the nasal pair are separated for about one-fourth of their 

 length by the upper premaxillary limbs. The front termination of the 

 bone is but slightly in advance of the anterior end of the narial 

 opening. The contact with the maxillary is effected by a process 

 running forward from the lachrymal contact, completing the enclosure 

 of the posterior end of the narial opening within the nasal. 



Lachrymal. Is wedge-shaped, twice as long as high, thickest 

 behind, thin toward the front. Is in contact with the nasal, prefrontal, 

 jugal, maxillary and premaxillary. Supero-anteriorly it is largely 

 hidden beneath the end of the lower premaxillary limb. Its posterior 

 border is protrudent and fully enters into the formation of the orbital 

 rim. Above its sutural union with the jugal it lies external to and 

 closely against the thin, elevated apex of the maxillary. In inner 

 aspect the bone is seen to owe its posterior thickness to the development 

 of an internal ridge which runs upward and slightly backward from 

 the hinder end of the jugal contact and is prolonged thinly above 

 between the nasal and the prefrontal. This ridge has a large per- 

 foration which marks the passage forward of the lachrymal canal. 



Premaxillary. Consists of an anterior portion expanding out- 

 ward from which are given off a long lower limb and a relatively short 

 upper limb. The lower limb passes back over the maxillary and- 

 terminating narrowly overlaps the lachrymal and nasal. The two 

 upper limbs separate the nasals anteriorly. The front border of the 

 anterior expansion is recurved, roofing over an extensive cavity which 

 opens backward on to an unevenly depressed floor. The bone does not 

 anywhere attain any great thickness. The two premaxillaries together 

 have an anterior breadth apparently little less than the maximum 

 posterior breadth of the skull. 



Jugal. Is long, thin, and plate-like, obtusely angulated in lateral 

 outline below, and deeply emarginated above by the orbit and the 

 lateral temporal fossa. It connects antero-superiorly with the 

 lachrymal, anteriorly with the maxillary, posteriorly with the quadrato- 

 jugal and the quadrate, and superiorly, behind its midlength, with the 



