OCR Text |
Show 1899.] CRANIAL OSTEOLOGY OF THE PARROTS. 45 the mandibular fenestra differs in the two genera, being obsolete Myopsittacus, but large in Caica. In Conurus and Pyrrhura the orbit is sometimes complete, though the suborbital bar when complete is slender ; when it is incomplete the postfrontal process is long, as long or nearly so as the squamosal and very much longer than in any of the Old-World Parrots. The squamosal process is curved below but indistinctly notched, the suprameatal process is extremely small, the auditory meatus is uncommonly wide and its posterior border is very near to the occipital ridge. The paroccipital processes are prominent and more vertical than in Chrysotis. The nostrils are of moderate size, rounded, and somewhat distant, being intermediate iu all three respects between Chrysotis and Myopsittacus. The interorbital vacuity is considerably larger than in Chrysotis or Pionus. The mandibular fenestra is variable, sometimes large aud sometimes obsolete. There remain to be considered a small number of genera between which I find it harder to draw osteological distinctions or to trace definite resemblances to those already considered. These forms include Palceornis, Tanygnathus, Eclectus, and Geoff royus-in other words, the remaining genera of the so-called Palosornithince after removing from that family Agapornis and the Australian genera allied to Aprosmictus; and also Pachynus and Brotogerys, at present grouped respectively with the Pionince and the Conurince, Pceocephalus, the African genus grouped with the otherwise exclusively South-American Pionince, and Coracopsis, associated by Salvadori with Psittacus. The above genera have all an incomplete orbit and an extremely small postfrontal process in the shape of a more or less vertical ridge. The prefrontal process is long, and it extends close to, though it is not united with, the tip of the long straight squamosal process. The auditory meatus is comparatively wide ; the area between it and the occipital ridge is broader than in Conurus or Chrysotis, but narrower than in Psittacus or the Lories, and a fortiori much narrower than .in Agapornis. There is no notch below (except in Coracopsis) nor groove across the base of the squamosal process. The skulls of Palceornis and Tanygnathus are extremely alike, the only conspicuous difference being in the nostrils, which in Tanygnathus are smaller and wider apart. In both genera the interorbital vacuity is extremely small and similar in character. In Eclectus the interorbital vacuity is moderately large, the squamosal process is expanded towards its tip, the nostrils are small and oval with the long axis of the oval vertical, and the descending occipital ridfe is faintly marked (whereas in the others it was extremely strong) and curves forwards, giving a distinctly different outline to the post-auditory area in front of it. In Geoffroyus, with no very important differences perhaps from Eclectus, there is less identity of characters than we should expect to find from the very close association in which it is customary to place the two genera. |