DR. w. w. Ely's notes on chapter ii. 297 



uncial process of the parietal, and a slight but more obtuse devel- 

 opment appears also in the European. 



" 8. In the beaver of the New World the end of the coronal 

 process of the lower jaw is slightly or not at all hooked, at least 

 not so strongly hooked as in several European. In all five lower 

 jaws of the American beaver the anterior opening of the canalis 

 infra-maxillaris lies under the alveolus of the anterior inferior 

 molar, in the European beaver somewhat before the same." 



In a lai'ge proportion of eases the coronal process of the lower 

 jaw in the American beaver presents the hooked form. It is some- 

 times very much hooked. The description given of the anterior 

 mental foramen correspond* with my observations. 



" § 4. Posterior aspect of the skull. 



" The general form of the squamous portion of the occipital 

 bone shows no essential variations. The middle portion of its 

 posterior surface shows in the American as well as in the Eu- 

 ropean a shallower or deeper, broader or narrower groove, or a 

 single, sometimes even doubled longitudinal ridge. 



" The occipital foramen, on the contrary, in all the European 

 skulls, is narrower than in the American, but appears extended 

 further upward than in the latter, so that its upper margin is 

 nearly on a level with the base of the zygomatic process of the 

 temporal bone, while in the American skulls the superior margin 

 of the occipital foramen lies about opposite the inferior border of 

 the zygomatic process. Correspondingly with the first-described 

 relation of the occipital foramen the squamous portion of the oc- 

 cipital bone over the occipital foramen appears in the European 

 skulls lower than in the American — an appearance especially 

 striking in the two skulls of equal size with the American skull 

 of Kuprianow " 



If we examine a large number of skulls of the American beaver, 

 the great variety of forms presented by the occipital foramen ap- 

 pears remarkable. It is sometimes low and broad, again a 

 rounded arch, and in other instances shows the high triangular 

 shape peculiar to the European variety. This form is found fre- 

 quently in young, and occasionally in old skulls. 



" § 5. Inferior aspect of the European and American skulls. 



" The groove occurring on tlie inferior surface of the base of 

 the occiput so characteristic of the species Castor, from three to 

 four lines deep, six to seven lines broad, posteriorly six to eight 



