366 11R. ST. GEORGE MITABT OTf THE SKELETON OF [MaV 7, 



The lateral surface of the prosopium in front of a vertical line 

 descending ventrad from the preaxial margin of each nostril is in 

 P. erithacKS slightly swollen and convex antero-posteriorly and 

 rather more so dorso-ventrally. It is slightly more convex in both 

 directions in L. Jfavoj)aUiatus, in which also the more posterior 

 portion of the side of the beak is less flattened than in P. en- 

 thacus. 



The ventral margin of the prosopium is, as already implied, 

 more sharply curved in front of the tooth. The tooth itself is 

 thus slightlv more prominent, and the tomial margin behind it is 

 slightly more convex than in P. erifhacus. 



Postaxially the tomial margin ends in what may be called the 

 jugal process {ji>). It is broader and more rounded from within 

 outwards, \^hile above it the concavity which receives the preaxial 

 end of the zygoma into it is much more marked in L. JJavopalliatus. 

 The jugal process itself extends relatively more postaxiad and 

 somewhat more ventrad than in P. enthaeus, so that the tomial 

 margin presents a slight concavity towards its postaxial end, 

 though very much less than that formed by the tooth and the 

 parts in front of it. The upper boundary of this concave margin 

 (which is the dorsal margin of the fossa for the zygoma) forms a 

 suprajugalar (sy) process much like that of P. erithacus ; but while 

 in the latter species the postaxial margin of the beak above 

 the suprajugalar process is postaxiall_y concave and terminates 

 dorsally in a small but distinct lachrymal process {Ip) — which is 

 received into the frontal beneath a slightly marked prominent 

 nasal process (njj) of the latter bone — in L. jiavopalliatus the 

 postaxial margin above the suprajugalar process is nearly straight, 

 and ends in a very minute lachrymal process, which more abso- 

 lutely coincides with the dorsal line of the cranium in this external 

 view of the skull than in the other species. 



In the latter, the lamina of bone which intervenes between the 

 apex of the lachrymal process and the nearest point in the post- 

 axial margin of the nostril is about as broad as two-thirds the 

 antero-posterior extent of the nostril, but in L. JlavopalUatus it is 

 slightly less than half this extent. 



The depth of the lamina of bone ventrad of the nostril to the 

 tomial boi'der is one-fourth less than twice the diameter of the 

 nostril. In P. erithacus it is only one-fifth less. 



The dorsal aspect of the prosopium has the outline of an 

 isosceles triangle, the apical angle \\hereof is of about 50° instead 

 of 40°, as in P. erithacus. Its base (the preaxial boundary of the 

 cranio-facial articulation) is straighter and does not so clearly 

 exhibit the curves (a very slight median conca^^ty with two shght 

 convexities external to it, external to which, again, are two con- 

 cavities each bounded externally by one of the lachrymal processes) 

 which there exist in P. erithacus. 



The lachrymal processes are relatively as well as absolutely 

 smaller, and instead of projecting strongly outwards as well as 

 backwards project backwards and but very shghtly outwards. 



