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Show 41 PROF. D'ARCY W. THOMPSON ON THE [Jail. 17, Psittacus, Coracopsis, and Dasyptilus, are very different from one another in regard to their skulls. Coracopsis appears to show a marked resemblance to Eclectus and Geoffroyus. As to Dasyptilus, it is certainly very different from both Coracopsis and Psittacus: the characters of our imperfect specimen suggest no close alliance with other forms, but go some way to indicate a very isolated position for the genus. The skull of Agapornis differs very materially from that of the typical Palceornithince. The difference is, in the first place, conspicuous iu the extremely narrow auditory meatus and extremely wide, almost square, surface between its straight posterior border and the descending occipital ridge. The suprameatal tubercle is moderately developed, the squamosal process long and curved, the postfrontal process extremely small, the nostrils and the interorbital and mandibular fenestra all'large. It is for one thing plain, from the breadth of its post-auditory region, that Agapornis differs greatly from the ordinary South-American Parrots. I regret that 1 have not been able to examine the skull of Psittacula, for it would be extremely interesting to see whether this osteolognal feature confirms (like the characters of the carotids) the separation of these two superficially similar but geographically distinct genera. Extremely different from all the Parrots of the Old World and very similar to one another are the two genera Chrysotis and Pionus. ' The orbit is complete by junction of the prefrontal and postfrontal processes, and the bridge of bone so formed descends to form an angular prominence opposite the extremity of the squamosal. The temporal fossa is extremely narrow. The inferior border of the squamosal is curved but not notched. The suprameatal tubercle is low, the auditory aperture wide, and its posterior border is very near to the occipital ridge which bends forward in a sinuous curve to approach it. The paroccipital processes are prominent but flattened or excavated below externally to the basitemporal ridges. The nostrils are of moderate size, the interorbital fenestra? small, and the mandibular fenestra nearly obsolete. Of the genera grouped with these by Salvadori under the name Pionince, I find Pachynus, Caica, and the African Poeocephalus to be very different. Caica, in the extremely small size, circular form, and wide distance apart of its nostrils, resembles Myopsittacus, which latter is usually grouped with the Conures. In their other characters Caica and Myopsittacus are very similar to one another. The postfrontal process is short and nearly vertical, especially in Caica. The squamosal process is curved in its lower border and more or less distinctly notched at its base. The suprameatal tubercle is distinct, the auditory meatus rather wide and its posterior border somewhat further from the occipital ridge than in Chrysotis and much farther than in Conurus. The paroccipital process is very much as iu Chrysotis; the long prefrontal process much as in Conurus. The interorbital fenestra is of moderate size |