62 ME C. W. ANDEEWS ON THE SKULL AND 



region is very great, and examination of it in this bird on the whole tends to support 

 the views previously put forward. 



The pterygoids (j)t.) are stout, laterally compressed bones, of considerable depth. At 

 their posterior end they bear a cup-like depression, which receives a corresponding 

 tuberosity on the inner border of the quadrate, and on their upper border, one-third 

 of their length from the posterior end, there is a stout process, oval in section and 

 projecting backward, upward, and inward ; it terminates in a facet, which articulates 

 with a corresponding surface on the base of the skull. These upper processes of the 

 pterygoids occupy the position, and perform the function, of the basipterygoid processes 

 of some birds. Anteriorly the pterygoids converge and just meet below the rostrum: 

 their anterior ends are abruptly truncated at right angles to their long axis, and form 

 facets for articulation with the palatines ; these latter are very large bones ; posteriorly 

 they bear short, broad pterygoid processes, which meet in the middle line and articulate 

 with the pterygoid facets just mentioned. The median union of the palatines extends 

 forward about 3 cm., and is marked by a slight ridge : in front of this their median 

 borders diverge and are notched by the hinder borders of the internal narial slits. In the 

 interval between the palatines no trace of the vomer is preserved, except that close to the 

 anterior end, where they join the maxillo-palatine plates, there are traces of a median 

 plate, which is probably a portion of that bone. The body of the palatine is very large, 

 and consists of two lamellae separated by a deep valley and projecting almost vertically 

 downward. Of these the outer is much the larger, and forms a great ventrally- 

 directed flange. Its inferior border is somewhat thickened, and meets the posterior 

 border, which also is thickened, nearly at right angles. The angle thus formed is slightly 

 everted, and a short distance above it the posterior border slopes gently backward to 

 the pterygoid process. The inner lamella is very small ; its ventral border is thickened 

 and is continued backward to meet its fellow on the middle line, forming the median 

 ridge above noticed. 



The anterior portion (maxillary process of the palatine is formed by the widening out 

 of the external lamella; this fuses with the maxillo-palatine plates, and together with 

 them forms the prominent longitudinal rid<^e projecting below the level of the tomium, 

 as before described. The bird in which the palate most nearly resembles the fossil 

 in this respect is Diomedea, in which the disposition and relative proportions ot these 

 ridges and the form of the cutting-edges of the beak are very similar. Dorsally 

 the palatines send up a thin triangular plate of bone on either side of the rostrum and 

 embracing it. 



The quadrate (Plates XIV. and XV. fig. 1, also text-figure, p. 63) articulates with 

 the skull by two distinct condyles sharply separated one from another by a deep pit, 

 at the bottom of which is a large pneumatic fossa, hollowed out in the neck of 

 the bone. The antero-external capitulum (O.H.) is much the larger ; it is triangular 

 in outline, convex from above downward, and slightly concave from side to side The 



