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Show 38 PROF. D'ARCY W. THOMPSON ON THE [Jan. 17, cus (figs. 38, 39), and Melopsittacus (fig. 40, p. 39). Of these, the last alone differs markedly from the others. The characters common to the rest are precisely the characters to which I have called attention in Aprosmictus, Polytelis, and Pyrrhulopsis; that is to sav, to the Australasian forms described under the group Palce-ornithince. In all, we find an incomplete orbital ring, a postfrontal process scarcely represented by more than the raised border of the orbit; a squamosal process crossed at its base by a deep groove above the meatus and in front of the suprameatal process. In all, the auditory meatus is narrow and curved ; the intraorbital vacuity is large (especially in Nymphicus); the mandibular fenestra is obsolete. In all, the base of the skull is flattened, the small tri- Fig. 38. Nymphicus uvceensis. Fig. 39. Auditory region of Nymphicus uvceensis (enlarged). angular basitemporal plate being nearly on a level with the areas at its sides. The squamosal region presents certain peculiarities in the several forms. In Platycercus, at least in Pennant's Parrakeet, the groove above described at the base of the squamosal is bridged by a well-developed ring of bone, extending from the suprameatal process to a slight descending process or tubercle at the base of the squamosal. In Nymphicus the groove is extremely deep, and though the bridge of bone is not present, the two processes are very wrell marked, that at the base of the squamosal being extremely conspicuous. Iu Neophema the postfrontal process is at a minimum, the posterior border of the orbit running with |
