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Show 388 DR. ST. GEORGE MIVART ON THE SKELETON OF [May 7, both the sympbysial 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. erithacus and less so in L. flavopalliatus. 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. In P. erithacus there is a depressed transverse area (*7 m m . 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. flavopalliatus 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. flavopalliatus, because in that species the symphysis is so much longer compared with the total anteroposterior extent of the mandible. From each pair of foramina a groove runs backwards and inwards till it meets its fellow of the opposite side, from which point a single groove runs downwards and backwards to the middle of tbe 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. flavopallicdus. 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. W h e n 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. flavopalliatus, while the concavity 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 symphysial 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. flavopalliatus it is a very open elliptical arch and less strongly concave (see figs. 16 & 14). Its middle point is relatively very much nearer one between tbe 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 |