| OCR Text |
Show 32 PROF, D'ARCY W. THOMPSON ON T H E [Jan. 17, plete, and in all these the postfrontal process is extremely reduced, forming only a short protuberant edge as in Eclectus. ' In all the squamosal process is well developed : it is especially long and straight in Pachynus, in which it nearly meets the prefrontal; the latter process is much shorter in Pceocephalus than in the other two. In Pachynus the basitemporal ridges are faint, and the surfaces external to them and extending back to the paroccipitals are much flattened, the paroccipitals being directed backwards ; there is no trace of descending maxillary processes. In Caica the basitemporal ridges are much stronger; in all the basitemporal plate is nearly on a level with the occipital condyle. The auditory meatus is somewhat narrower and more notched above and below than in Chrysotis, and the interspace between it and the occipital ridge is somewhat greater. The quadrate in Caica and Pachynus has a high posterior prominence above and behind the socket for the jugal, as in Conurus. The mandibular fenestra is large in Caica, small or obsolete in the other two. Family PSITTACIN^E. The skull of Ps. erithacus has been considered already. I have also studied the skulls of Coracopsis vasa (fig. 27) and C. nigra, and an imperfect specimen of Dasypiilus pjecqueti (fig. 28). Coracopsis vasa. The skulls of these Parrots bring us face to face with the problem of whether Coracopsis and Dasyptilus are rightly placed in so close a relation to Psittacus; in other words, with one of the dubious and crucial questions that osteology might suffice to solve. 1 cannot boast of being able to give a very clear answer to the question, but it seems to me that the skull of Dasyptilus, and in a minor degree that also of Coracopsis, differs iu so many points from that of Psittacus, that they go far to show that the little group of Psittacince is very dubiously or improperly defined. In Coracopsis vasa the postfrontal process is almost obsolete forming a slight vertical ridge behind which rises the impression of |
