( 125 ) 



GenefwVl (.'omi'ARIsons. 



The ijeculiarities of the skull of Palaeocorax, though not perhaps very sti-ikiiig, 

 will be the more easily apparent, and their siguificaace the more readily perceived, 

 if we take a brief survey of the skulls of the Corvidae in general iu so far, at any 

 rate, as they present characters bearing on the main theme of this paper. 



As touching the parietal region of the skull, it will be remembered that 

 differences iu the "temporal fossa" were pointed out wherein the skulls of 

 Palaeoccrax differed from that of the Raven. These differences concerned the 

 form of the " scars " or depressions for the temporalis and dennotemporalis 

 muscles, and au examination of a series of skulls belonging to different genera of 

 tlie Corvidae shows that these "scars," as well as the form of the processus ~ij(]o- 

 maticns squamosi exhibit many slight differences of form, which, apart from their 

 morijhological value, may prove useful characters for systematic ptirposes. Aud 

 the same remarks apply to the anterior palatal vacuity. 



As touching the parietal region of the skull, the chief differences presented 

 are to be foand iu the relative size and shape of the postorbital process and the 

 processus z^//omaticus squamosi, and in the muscle-depression for the temporalis. 



Only among the Corvidae is the postorbital process well developed. In 

 Coleiis, Pica, (Jarridus, Sucifraga, Deiidrocitta, Urocissa and Psilorhinus it is 

 much reduced, in some cases almost to the vanishing-point. 



An ossified nasal septum apparently occurs only in Palaeocorax, Macrocorar, 

 Corcidtur, and in Corcus scapidatus and C. amcricanus. 



In regard to the vomer, though the range in relative size and shape is not 

 great, it yet presents some noteworthy characters. It presents its maximum iu 

 Palaeocorax (p. 123), while in Cordis scapidatus, Psilorhinus mcxicaiius, and 

 Urocissa mag/iirostris it is extremely wide anteriorly. On the other hand it is 

 much reduced in Corcus frugilegus, Macrocorax, (jarrulus, Coleus, Pica and 

 Nuci/raga ; iu the last-named genus the free eud is rounded instead of notched — 

 a further stage in degeneration. 



The maxillopalatine processes, like the vomer, present noteworthy characters. 

 As with the vomer, they present their maximum development in Palaeocorax, 

 wherein they are of great width (p. 12:3). In no other member of the Corvidae is 

 the maxillopalatine so wide, or are the backwardly-directed spurs — the maxillo- 

 palatine processes — so large. In the matter of these processes, however, an 

 apju'oach is certainly made in the case of Coreus frugilegus, in Psilorhinus mexi- 

 canus, and in Corcultur crassirostris. At the other extreme we find Nuci/raga and 

 Corvus scapulatus, wherein these rods are long and narrow and imperfectly ossified 

 at their free end, as well as Dendrocitta, Urocissa, Garrulus, Coleus and Pica, 

 wherein varying stages of reduction may be traced. 



The lachrgmal is unfortunately missing iu most of the skulls herein described; 

 happily it has been preserved in some. It ajjpcars to attain its maximum in 

 Corcus scapulatus, C. macrorhgncha and Garrulus glandarius, and reaches its 

 minimum in Coleus monedula. In the first-named species it is roughly C-shaped, 

 the interior limb being much swollen and projecting beyond the autorbital 

 plate so as to rest on the quadrate-jugal bar. In Psilorhinus, while of the same 

 shape the interior limb is more or less spatulate, and does not reach the interior 

 border of the autorbital plate. Corcus amcricana agrees with Psilorhinus in this 

 respect, but the spatulate end is much swollen. In Corcus comix both extremities 



