388 DE. ST. GEORGE MIVAET ON THE SKELETON OF [Maj 7, 



both the symphysial convexity passes smoothly into the relative 

 flatness of the adjacent external surfaces of the beak-bearing parts 

 of the lateral rami, without any dorso-ventral ridges dividing it 

 from the latter. The front, or external, surface of the symphysis 

 is beautifully marked with vascular grooves in P. erithaciis and less 

 so in L. jlavopaUiatus. The apex of this surface is dentated or 

 somewhat irregularly serrated in both, but the transverse extent 

 of this serrated margin is less relatively as well as absolutely in 

 L. flavopalliatus. lu P. erithacus there is a depressed transverse 

 area (•? mm. long x "12 broad) just below the serrated margin and 

 •a number of small foramina open into this area (see fig. 19, p. 393). 

 In L. flavopalUatus there is no such depressed area, though there 

 -are small foramina close to the dorsal margin of the mandible. 



At a short distance from the dorsal margin, two small foramina 

 open on either side of the symphysis, the two pairs being about as 

 distant from each other as from the dorsal margin of the mandible. 

 They are relatively much nearer the dorsal than the postero-ventral 

 margin of the mandible in L. flavopalUatus, because in that species 

 the symphysis is so much longer compared with the total antero- 

 posterior extent of the mandible. From each pair of foramina a 

 groove runs backwards and in'nards till it meets its fellow of the 

 opposite side, from which point a single groove runs downwards 

 and backwards to the middle of the postero-inferior symphysial 

 margin. Thus a Y-shaped groove is formed. The two upper arms 

 of the Y meet at a much more open angle in P. erithacus than 

 in L. flavopalUatus. Their point of junction also in the former 

 species is at about the dorso-ventral middle of the symphysis, while 

 in the latter it is distant from the postero-inferior margin only 

 one-third of the total dorso-ventral extent of the symphysis. 



When the mandible is viewed laterally, its supero-anterior 

 margin presents, in P. erithacus, a strongly marked concavity 

 bounded in front by the apex of the mandible and postaxially by an 

 obscurely marked process I have called the dentary process (d). 

 The process is still less marked in L. flavopalUatus, while the con- 

 cavity between it and the mandibular apex is but slight and so 

 presents a great contrast to that part in the other species. In both, 

 a faintly marked more or less undulating ridge proceeds downwards 

 and backwards from the dentary process to the ventral margin of 

 the ramus, and this marks the limit of the postaxiad extension of 

 the bony beak. 



The posterior margin of the sj-mphysial portion of the mandible 

 is very different in the two species. In P. erithacus (fig. 17) it is 

 in the form of a pointed arch, neither acute nor obtuse, but in 

 L. flavopalUatus it is a vevj open elliptical arch and less strongly 

 concave (see figs. 16 & 14). Its middle point is relativelv very 

 much nearer one between the anterior ends of the inferior articular 

 surfaces, because the symphysis is relatively so much longer in this 

 species. 



The postero-superior surface of the symphysis is strongly concave 

 transversely, but only very slightly so antero-posteriorly in both 



