MR. W. K. PARKER ON THE OSTEOLOGY OF BAL^NICEPS REX. 299 



This is almost the whole function of this groove in the Adjutant and many other 

 birds, the dental margin at its posterior part being, in a manner, pushed up high by the 

 action of the mandibular ramus; whilst in the anterior part of the upper jaw the groove 

 is obsolete, and the mandible lies wholly under the maxilla. 



This may be seen in the curious jaws of the Spoonbill : but in the Boat-bill the man- 

 dible passes within the zygoma, at the junction of the dentary with the surangular, and 

 then soon liberates itself, adapting its margin very accurately to that of the maxilla ; and 

 this latter bird has no trace of this submarginal groove with its internal ridge, its hard 

 palate being as simple as that of the Giant Goatsucker (Podargus humeralis). 



In the Heron, which has a subterminal notch to the horny sheath of the maxilla, and 

 very elegant lozenge-shape recurved horny teeth along the sheaths of both maxilla and 

 mandible, the jaws fit together as in the Adjutant. But in the former bird submar- 

 ginal ridges may be seen, faintly in the bone, clearly in its horny sheath, running along 

 the posterior three-fifths of the hard palate, nearer the dentated margin than the mesial 

 sharp ridge, but rather parallel with the mid-line than with the margin. In the ante- 

 rior half of the hard palate of the Spoonbill, and in that part of the mandible adapted 

 ,to it, a similar, rather faint ridge may be seen, running somewhat concentrically to the 

 outline of these spatulate jaws. 



In the Pelican (P. onocrotalus) the hard palate is subdivided into a broad mesial 

 and two narrower marginal portions by two strong ridges, the mid-line being gently 

 and evenly concave, and marked with large oblong passages. 



These marginal portions, narrow behind, but becoming gradually broader towards 

 the somewhat spatulate anterior part of the jaw, are strongly scooped, or concave; and 

 in these concavities the mandibular rami lie, in the closed condition of the mouth. 

 This scooping of the hard palate reaches nearly to the mid-line in the Flamingo, the 

 mesial part of the hard palate in this bird being merely a rounded keel. Into these 

 nearly semicylindrical spaces the round, thick, upper and inner parts of the mandibular 

 rami are accurately fitted. 



If space would permit, all these manifold but, anatomically, gentle modifications of 

 structure might be explained and their final purpose illustrated ; but every intelligent 

 naturalist will at once see their meaning in the habits of each bird. Undoubtedly the 

 Balseniceps comes nearest to the Turtle in this part of its structure, notwithstanding 

 the diflerence of function of the homologous parts. These secondary ridges give per- 

 fection to the beautiful dentated shears of Turtles, so well constructed to "graze the 

 sea-weed, their pasture"; whilst the additional maxillary ridges of this large-headed 

 Heron, the Balaeniceps, serve to break the spine of its finny prey. 



Ethmoid. (PI. LXV. fig. 1, npg.) 

 The anterior portion of that mass of bone in the Ostrich which Professor Owen calls 

 the connate 'prefrontals' (Rep. on Archet. p. 190. fig. 8. no. 14) is in the Balaeniceps, 



