384 



caudal vertebrae are well developed with thick and rough extremities. The spine of the sca- 

 pula and the long and bifid acromion are bent downwards. The slender clavicular bones are 

 preserved : they are joined by long ligaments to the ' manubrium sterni.' There is a wide 

 vacuity between the condyles of the humerus. The cranium of this species differs from that 

 of the Asiatic and Java Porcupines in the greater expanse and rounder termination of the 

 posterior ends of the nasals, and the corresponding ends of the premaxillaries are more 

 pointed than in the Java species. The facial part of the lacrymal is very small. The poste- 

 rior border of the lower jaw is straight, as in the Asiatic Porcupine. 



Purchased. 



Genus Erithizon. 



2114. The skull of the young Canada Porcupine (Erithizon dorsatum). 



The last molar is in place, and the deciduous molar is retained : the germ of the premolar 

 is exposed in its formative alveolus in both jaws. The greater part of the sagittal suture, as 

 well as of those between the parietal, interparietal, and superoccipital bones, have been obli- 

 terated, and the elements of the occipital have coalesced. The squamosal remains distinct 

 from the petrotympano-mastoid, which has been removed from the left side. The upper 

 surface of the frontals forms almost a flat square platform, bounded laterally by a well- 

 defined superorbital ridge. The antorbital vacuities are very large : their lower boundary 

 extends almost directly outwards. A short and narrow bony palate is perforated at its 

 middle by two foramina. The prepalatine foramina open into a large common fossa. 



Hunterian. 

 The following are parts of the same skeleton : 



2115. The atlas. 



The short, but broad, transverse process is perforated both horizontally and vertically by 

 the vertebral artery, which afterwards perforates the neural arch. 



2116. The axis and third cervical vertebra. 



These have coalesced at the summits of their neural arches, although the centrums remain 

 distinct ; and the epiphyses still intervene, both between the third and second vertebrae and 

 also between the body of the axis and the odontoid process. 



2117. The four succeeding cervical vertebrae. 



The seventh is distinguished by the non -expansion of the pleurapophysial part of its per- 

 forated transverse process. 



2118. The six anterior dorsal vertebrae. 



In most of these the line of union between the centrum and the neural arch may be seen, 



