OCR Text |
Show 1899.] CRANIAL OSTEOLOGY OF THE PARROTS. 37 not overhang the quadrate, but is excavated to form a deep notch, which exposes the head of the quadrate bone. In all these forms the intraorbital fissure is large, the descending processes from the hinder border of the maxillae are large also, the inner head of the quadrate is quite distinct, and the mandibular fenestra is obsolete. Fig. 36. Ayapornis roseicapillus. In all, the auditory aperture is much narrowed, by the forward growth of the posterior wall of the meatus; this takes place to the greatest extent in Polytelis and Aprosmictus, in which last the aperture is reduced to a curved slit. The basitemporal triangle is very small in Pyrrhulopsis, and well defined from the areas at its sides ; the paroccipital processes, looked at from behind, are nearly vertical; in Aprosmictus they are more horizontal, and the lateral areas are accordingly more on a level with and less defined from the basitemporal ; in Polytelis the same tendency is still more displayed. In Agapomis the orbital ring is incomplete and the postfrontal extremely small, as in the forms last described. There is a notch at the base of the squamosal process, but the latter is not separated by a groove from the suprameatal; the conformation here is more as in Eclectus. The auditory meatus is narrow, and the intraorbital vacuity very large. The mandibular fenestra is large also. The quadrate is very delicate in form ; its two heads are fused, its shaft is very slender, and its anterior process small. Family PLATYCERCIN^;. Of this group I have examined skulls of Platycercus (fig. 37), Nanodes (Lathamus) discolor, Acophemapulchella, Psephotus, Nymphi- Fig. 37. Platycercus eleyans. |