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Show 22 PROF, D'ARCY W. THOMPSON ON T H E [Jan. 17, mentioned above) to bound a supratemporal fossa. We do not know whether this process is actually developed as a mere continuation of the prefrontal or as a posterior offshoot of the postfrontal, because postfrontal and prefrontal are in all Cacatuidae intimately fused ; but I am inclined to anticipate that examination of young individuals would show it to be an outgrowth of the postfrontal, and to correspond precisely to the posterior or squamosal ramus of that bone in the Lacertilia. Microglossia aterrimus (reduced). Fig. 13. Quadrate bone of Microglossus aterrimus. art., the accessory articular surface beneath the jugal cup for articulation with the edge of the mandible. The only Cockatoos in which I have observed this supratemporal fossa to remain incomplete are C. ducorpsi (fig. 14) and Microglossus aterrimus (fig. 12), and here we appear to have the posterior outgrowth or ramus of the postfrontal developed, though not to such an extent as to fuse with the squamosal process. Blanchard (C. R. 1856, p. 1098) says the same of Cah/ptorhynchus xaniho-notus, but in G. banksi (fig. 10), which I have examined, the fossa is complete and the whole region much as in other Cockatoos |