1899.] OSTEOLOGY OF THE prGOPODES. 1027 



when seen from below. From the dorsal aspect, the trough-like 

 region is found to be restricted to the posterior end, immediately 

 underlying tlie anterior end of the rostrum. 



The palatine (Plate LXXII. fig. 7), in its general form, and in its 

 relations with tbe vomer and maxillo-palatine processes, somewhat 

 closely resembles that of the A Icida;. It differs conspicuously from 

 that of the larger Tubinares iu its greater relative length, and in the 

 feebler development of the paired median and lateral keels formed 

 by the inner and outer borders of the palatine caudad of the maxillo- 

 palatine processes. Its general contour, from the ventral aspect, 

 may be described as rod-shaped, in front of the maxillo-palatines, 

 passing behind these into a shallow trough-like expansion. Seen 

 dorsally, the inner free edge of the expanded portion, cephalad, 

 rises dorsally into a scroU-shapea plate to articulate mesially with 

 the vomer. Seen laterally, this scroll-like dorso-lateral plate does 

 not fit closely up to the posterior border of an almost vertical 

 maxillo-palatine process as in the Tubinares, but leaves a large 

 space between. 



The pteryrjoid is rod-shaped, and more or less triangular in 

 section. That of the Colymbi sends outwards, from the outer 

 border of its extreme proximal articular end, a small plate to abut 

 against the base of the orbital process of the quadrate. Moreover, 

 it still further differs from that of the Podicipides, (1) in that it 

 possesses a strong inward curve, causing the pterygoids to embrace 

 the parasphenoidal rostrum, as in many Procellariae, from which 

 it differs, however, in that no glenoid articular surface is developed 

 for this purpose ; and (2) in that it sends foi'ward and upward, from 

 the external ventral border of its extreme distal end, a delicate 

 claw-like process, to embrace the articular end of the palatine — 

 or more con-ectly of the anchylosed hem iptery gold. This point 

 was first noticed by Coues (3). 



The quadrate more nearly resembles that of the Tubinares and 

 Impennes than that, of the Alcidse. It differs from all in the very 

 elongated and rod-hke form of its orbital process. Its otic and 

 squamosal heads are sharply divided. The glenoid mandibular 

 surface nearly resembles that of the larger Tubinares. Its external 

 condyle is hollowed from before backwards ; its internal condyle 

 may be divided into relatively large anterior and posterior facets, 

 meeting one another in the mid-ventral line. Immediately dorsad 

 of the posterior facet of the internal condyle is a sharply defined 

 pterapophysial facet for the articulation of the pterygoid. It is 

 non-pneumatic both in the Grebes and Divers, in which point it 

 agrees with both Impennes and Alcidae, and differs from the 

 Tubinares, in which it is pneumatic 



The Mandible. 



Is slender, elongated, and slightly recurved at the tip. It can be 

 more or less readily distinguished from that of other groups — such 

 as some Ai'deidae, which it somewhat closely resembles — by the 



