298 MR. W. K. PARKER ON THE OSTEOLOGY OF BALiENICEPS REX. 



between the coalesced ethmoidal pterapophyses — elements which seldom combine with 

 each other on the mid-line of the palate. The anterior largest passage just spoken of and 

 the smooth convex ridges are the anterior and lateral landmarks of these bones ; whilst 

 their posterior margin terminates on each side in a small, elegant spur of bone, the 

 point of each spur curving outwards, and each tip lying two lines from the deeply-grooved 

 posterior line of union of the two bones. The palatals at their inner margin articulate 

 with these palatal elements of the ethmoidal sclerotome'. 



This descending portion of the hard palate is easily understood by means of these 

 landmarks, and by a careful comparison of their unusually developed condition in the 

 Baleeniceps with the skulls of birds in which ossification has not proceeded so far. The 

 Adjutant, the Heron, the Duck, and the Common Rook, all help to explain these 

 homologues of the cornua attached to the lower parts of the ' vomer ' of certain 

 Chelonia, and of the turbinals of the Lacertian and Ophidian. 



The pterapophyses of the ethmoid have united along the mesial line of the palate in 

 the Adjutant (Leptoptilus) , in the Cancroma, in the Great Goatsucker {Podargus hume- 

 ralis), in the Merlin (Falco cBsalon), but not in Aquila chrysaetos nor in Accipiter nisus, 

 or in the Vulture. This floor of the ethmoidal neural space is complete beneath in the 

 Kingfishers (Dacelo and Alcedo) and in the Spoonbill and other birds with large man- 

 dibles. In most birds, however, they do not meet raesially, and in the Ostrich group 

 they are feebly represented. The condition of these parts is very exquisite in the 

 smaller Fissirostres, e. cj. Caprimulgus europceus — a good subject for the examination of 

 an ossified true ' ethmoid,' and of these pterapophyses of the ethmoidal sclerotome. 



At one-eighth of an inch external to tiie outer margin of the palatines of Balaeniceps, 

 a strong groove is scooped in the upper jaw, shallow at first, where it divides the 

 angle of that bone into an outer larger and an inner smaller portion ; it passes 

 forwards, gradually rising within the sides of the hard palate, until at the anterior 

 fourth it is midway between the margin and the mesial sinus. It then passes forwards 

 to the base of the great beaked tip, where it meets the grooves already spoken of on 

 the upper surface. 



Seen from beneath, the upper jaw of the Balaeniceps, from its elegantly curved outline, 

 suddenly narrowing towards the tip, its submarginal grooves, at first parallel, and 

 then taking a sigmoid curve inwards, to become nearly parallel again as they blend with 

 the margin, and lastly, the mesial sinus with its transverse dendritic branches, — is cer- 

 tainly an object of great beauty. Before leaving this part, we may notice that the bifur- 

 cating vascular grooves passing from the mesial sinus open into a smaller lateral sinus 

 which burrows the interior sharp edge of the great submarginal sigmoid groove. This 

 great groove at its posterior end cuts away, as it were, part of the angle of the 

 maxilla, to allow the mandible to fit tighter and to lock itself into the upper jaw ; and 

 the interior portion of the angle is thus always on a lower plane than the exterior. 



' We have not been able to detect any separate osseous centre for these elements ; they are evidently mere 

 outgrowths from the maxillaries, and are the homologues of the inferior turbinals of Mammals. 



