228 



VERTEBRATES. 



point of the beak, giving the skull a slightly oblique, 

 pyramidal form, the cranium forming the base of the 

 pyramid. 



The skull is composed of many bones, a large proportion 

 of which will be found to be solidly coossified in all except 



immature specimens. Their out- 



lines will not be distinguishable, 

 5 



but their location may be learned 

 by reading the following descrip- 

 tion with skull in hand. 



The region immediately sur- 

 rounding the foramen magnum 

 is formed of the occipital bones. 



Four pairs of bones complete 

 the dorsal surface of the skull. 

 The bones of each pair meet on 



the median line. 



^ The parieM bmes f orm the 



greater part of the roof of the 

 cranium, and present convex dor- 



sal SUrf aCCS. 



2 - In front of these ' 



SKULL OF SPARROW, slightly 

 enlarged (ventral view, man- 

 dible removed) : m, foramen 

 magnum; c, occipital con- 

 dyle; bs, basisphenoid ; r, 



bar ; q, quadrate ; ptg, ptery- 



lary portion of quadratojugai tal bones cover the foremost part 



ptpaSeTroc^'o/^ of the cranial cavity, and form 



maxillary; pr m, maxillary the upper boundary, and most of 



SStSTSSSfLS the posterior boundary, of the 



cranial cavity (closed in life orbits. 



3. The nasal bones lie next in 



front of the frontals, and extend forward between, and 

 partly surround posteriorly, the nasal openings. 



4. The premaxillary bones complete the dorsal surface, 

 and form the bony part of the upper mandible. 



Looking at the side of the skull, note : 



1. The lachrymal bone, of irregular rhomboidal outline, 

 set transversely to form the anterior wall of the orbit. 



