1026 MB. w. p. PTCRArT ON a?HE [Dec. 19, 



TJie Premaxilla, Nasal, and LacTii'ymal. 



The naso-premaxillary region of the upper jaw bears a strong 

 superficial resemblance to tbe Alcidoe on the one hand, and certain 

 genera ot" Penguins on the other, e. g. that of Megaeudyptes. It 

 may readily be distinguished from the former by the form of the 

 nostrils, which are schizorhinal in the Alcidae ; from the latter, apart 

 from the rest of the skull, it would be difficult to distinguish it. 



The nasal, in the adult, both in the Colymbi and Pygopodes is 

 completely fused with the premaxilla and frontals. In the Divers 

 it is, furthermore, fused with the outer border of the lachrymal. 

 It is not deeply cleft caudad, the form of the external narial 

 apertures being holorhinal ; they are also, by the way, in the dried 

 skin pervious, there beiug no nasal septum. 



The lachrymal is a fairly large bone in the Colymbi, with a 

 peculiar notch in the posterior border of its free end ; in the 

 Podicipides, as elsewhere remarked (pp. 1024, 1031), it shows signs 

 of degeneration. 



The Maaiillo-jugal Arch. 



The maxilla, in the adult of both Grebes and Divers, is indis- 

 tinguishably fused with the premaxilla. The maxillo-palatine 

 processes are Charadriiform in type, closely resembling those of the 

 Alcidpe, being leaf-shaped, and in the Colymbi more or less 

 fenestrated. The antrum is very shallow. They are widely 

 separated in the middle line, and the palate is therefore schizo- 

 gnathous. 



The form of these processes rather closely resembles that of 

 the smaller Tubinares, e. g. Felagodroma, Procdlaria, but difFers 

 markedly from that of the larger forms, such as Pvffimis for 

 instance. In these, it will.be remembered, the maxillo-palatine 

 processes do not extend baekwai'ds into the lachry mo-nasal fossa, 

 and are hollowed out to form a spacious antrum of Bighmore. 



The anterior end of the maxillo-jugal arch does not trend upwards 

 to meet the lachrymal, as in many Procellariidoe, bat the lower 

 limb of the lachrymal in the Colymbi is very long, so much so as 

 nearly to touch the bar, and thus to completely shut ofp the 

 triangular lachrvmo-nasal fossa from the orbit. The greater part 

 of this arch is made up by the quadrato-jugal bar. 



The Vomer, Palatine, and Pterygoid. 



The vomer in the Colymbi appears to be free throughout life ; 

 in really adult or advanced Podicipides it fuses with the palatines. 



In the Colymbi it somewhat closely resembles that of the 

 DiomedeidiB, appearing knife-shaped from below and provided 

 w ith a pair of lateral wings along its dorsal border. It differs 

 from this type, however, in that it lacks the conspicuous dorso- 

 ventral curve. Its dorsal aspect is trough-like, and posteriorly 

 lodges the anterior end of the parasphenoidal rostrum. 



In the Podicipides it is knife-like, and lacking the lateral wings, 



