230 VERTEBRATES. 



quadratojugal bar, but irregular, widely and irregularly 

 expanded in its anterior part, and bent inward to fit 

 against the rostrum. 



The two bones composing this bar are readily distin- 

 guishable. The palatine is the broad, flat, anterior one 

 which meets the rostrum by its inner edge. The pterygoid 

 is the slender, posterior one, which has its inner end ex- 

 panded to fit against the side of the rostrum, its outer end 

 rounded for articulation with the quadrate. 



Thus it will be seen that both upper and lower mandibles 

 are articulated to the cranium by the quadrate. The other 

 attachment of the upper mandible to the cranium is in the 

 region of the nasal bones. Holding the cranium between 

 the fingers, gently move the mandible up and down, and 

 observe that the flexibility of the bones in this region, 

 and not a distinct articulation, permits this motion. While 

 moving the mandible, observe that the palatine and ptery- 

 goid slide forward and backward upon the rostrum, and 

 the lower exterior corner of the lachrymal slides upon the 

 maxillary. 



A pair of minute bones (the vomers) meet on the median 

 line between the palatine processes of the two premaxil- 

 laries, and in front of the two palatine bores. These are 

 liable to be removed in the preparation of the skull, and 

 so may not be found. 



II. The Spinal Column. Study the spinal column. 

 Note the length and flexibility of the neck, the shortness 

 of the tail, and the large number of anchylosed vertebra 

 which meet the bones of the pelvic arch. 



Four regions are distinguishable in the spinal column, 

 but the boundaries between them are ill defined. Named 

 from the front, these are the cervical, thoracic, sacral, and 

 caudal regions. 



The cervical vertebrae are those between the head and 

 the foremost vertetra bearing a rib articulating with the 



