THE AMERIC.W .\ A l( ' R A 1 .1 S I. [\ . m . WW | | I. 



pedicle, its convex surface bciiii;- inferior. \\'e shall see further 

 on that this posterior aspect of a dix er s skull resembles much 

 less the same view of the skull of any of the Larida^ than Alca 

 does ; indeed, the posterior vie\\- of the skull of the razor-bill 

 very closely resembles a like view of the skull in several of the 

 gulls. 



On the under side of the skull of L 'rinator Inmmc we find 

 the arrangement of the palate and other elements agreeing in 

 all essential particulars with the gulls, auks, or guillemots ; in 

 other words, its structure is that of a typical cecomorph of 

 Huxley's classification, so far as these parts are concerned. 



In a well-cleaned skull the palatines can easily be traced to 

 their anterior endings, and this is equally true of I', imbcr. 

 Behind they are long and narrow, showing a double carination 

 with a concavity dividing them. This is again divided by a 

 transverse ridge near the middle of the body of each bone' on 

 its under side. The ascending processes of the palatines are 

 embraced by the hinder ends of the vomer, and between them 

 both rides the thin inferior edge of the rostrum. Anteriorly 

 the vomer among the Urinatoridae is more or less pointed, while 

 above it is longitudinally grooved for its entire length, and the 

 edges of this groove are well curled outwards. 



The maxillo-palatines are thin concavo-convex plates raised 

 above the horizontal portions of the maxillaries, and otherwise 

 arranged as in the Alcidae and I.arid^. 



The posterior heads of the palatines are in contact, and form 

 a groove between them above for the rostral bar of the presphe- 

 noid. They are embraced in a peculiar manner by the anterior 

 ends of the pterygoids, which are fashioned like little two-toed 

 feet to hold them, the larger claw being above and the smaller 

 one below, the seizure being of such a nature as to limit the 

 motion to a fore and aft one. Coues noticed this arrangement 

 in the loon, and alludes to it in his memoir. The posterior end 

 of each pterygoid is much enlarged and make^ an extensix e artic- 

 ulation with the quadrate of the corresponding side. 



The foramen ovale opens laterally in the red-throated diver, 

 and still more so in the loon, and the posterior wall of cich orbit 

 is marked by an outwardly concave. nearl> xertieal ridge, uhich 



