OSTEOLOG]- OF PVGOl'Oni: 



-'7 



ess, and two prominent facets upon its mandibular toot, at about 

 the same level. 



Regarding the skull of any of the I' i inatoi ida- from abo\ e, 

 the most striking features are the deep. sbarpK -detiued, supra- 

 orbital glandular depressions. These are e\leusi\el\ perforated 

 by minute foramina over their posterioi bakes, while a large 

 irregular foramen occurs at each anterior eiul. Over the fn.n- 

 tals they are se])arated by a thin crest of Ix.ne in the median 

 line, while their posterior halves curve regularU outwards, to 

 extend upon each roofdike post-frontal i)rojection. in I', iuibcr 

 we find them giving rise to a raised su])erioi- orbital margin, 

 connecting the lacrymal and the aforesaid post-frontal ])rojec- 

 tions, as in Alca and Uria. In [-nnator lummc this rim is 

 sometimes incomplete. Fully as marked as these sui)raorbital 

 depressions are the extraordinary crotaphyte fossx. These are 

 very broad antero-posteriorly, and strongly-marked throughout. 

 On the top of the skull they are separated by a raised median 

 line of bone, being the simple backward extension of that 

 smooth central area of the vault, which has remained unmuti- 

 lated by depressions. From this these fossa' sweej) on either 

 side in increasing depth downwards and forwards beneath the 

 overhanging post-frontal roof and over the top of the external 

 auditory wing. 



In a specimen of T. ivibcr belonging to the I'. S. National 

 Museum (No. 18256) I find the sui)erticies of the su])erior orbi- 

 tal margins very much roughened. In the middle line there is 

 also a "parietal foramen" at the hinder termination of a longi- 

 tudinal gutter that extends as far forwards as the thin (rest 

 dividing the supraorbital glandular depressions. 



Viewing the skull of the red-throated diver from behind wc 

 find that the large domedike supra-occi])ital prominence is over- 

 lapped by these broad crotajdiyte fossa, and the median line 

 separating them is extended directly backwards as far as the 



that separates the crotaphyte fossa: from the occipital area. 

 The plane of the foramen magnum is nearly vertical, and the 

 reniform condvle i)roiect> directlv liackwarO from a thick-set 



