( 126 ) 



are spatnlate and slic;litl_v swollen. In L'rocissa and Pica it is almost oolnmnar, 

 constricted in the middle, and greatly swollen. In jS'uci/raffa the inferior limb is 

 laterally expanded to form a large swollen cushion projecting on to the qnadrato- 

 jngal bar. In Colcus, which closes this series for tlie present, this ossicle takes 

 the form of a slender curved rod, extending downwards to reach the ipiadrato- 

 jngal bar. 



Another ossicle which demands mention here is that which was originally 

 fignred and described by AV. K. Parker in his monnmeutal papers on the palate of 

 the Aegithognathons Birds (T. Z. .S'.,vols. ix. and x.),aud called by him the " sej)to- 

 raaxilhiry." Occurring in pairs, he regarded them as " separated horns of the 

 vomer"; but I am not certain that their true nature has yet been determined. 



I find them well developed, and i|uite distinct, in Cortus americnnm and 

 Psilorliiiais mexicanus. In the last-named they occur as oblong plates extending, 

 one on either side, from the maxillo-])alatine jilate, immediately dorsad of the base 

 of the stem of the backward spur forming the maxillo-palatine plate, to the antero- 

 lateral angle of the vomer in the latter ; in Corvns the bitid extremity of the vomer 

 is produced beyond the ossicle. 



The Sternum. 



The sternum of Palaeocorax resembles that of the Raven, Cordis corar, but 

 may be distinguished therefrom by its smaller size, having a total length of 70 

 as again?t 70 — the minimum length of the sternum of the Raven— and by the 

 relatively smaller sj)ina externa. This in Palaeocorax has a relatively shorter and 

 more slender stem and is more sharply incised interiorly. The carina sterni in 

 Palaeocorax is relatively shallower, and does not terminate anteriorly, as to its 

 inferior border, in a point. The posterior notelies are relatively wider and shallower, 

 while the posterior lateral processes are relatively wider. There are but five 

 articular surfaces for the sternal ribs, as in tlie Raven. In the rapid widening of 

 the corjjun sterni immediately behind the last articular facet for the hindmost 

 sternal rib, Palaeocorax resembles Corrag ami'r/ca)i'is, though a similar widening, 

 it must be remarked, occurs in many of the Corvidae. 



The Shoulder Girdle. 



The J'urciila differs from that of the Raven, Corvus corax, in being smaller, 

 and in having the free ends relatively less expanded. The hypocleideum projects 

 markedly backwards in the middle line, and is inclined directly upwards and not 

 upwards and backwards as in the Raven. Finally the dorsal, concave aspect of the 

 fused proximal ends of the clavicles are marked by a deep groove. In the form of 

 the hypocleideum Palaeocorax recalls Corcus amcricaims and C. lomjirotitntin. 



The coracoid differs from that of the Raven in many minute characters too 

 subtle for description, but chiefly in the relatively large procoracoid process, in the 

 shallower depression for tlie lung head of the bici'ps, and in the feebler develo[imont 

 of the ridge dividing the areas of attachment of the supracoracoideas and coraco- 

 bracldaliis posterior ; further, the hamulate, in-turned area for the articulation of the 

 expanded end of the furcula is in Palaeocorax less developed. 



The scapula in Palaeocorax has its free end much more arched, and less tapering 

 than in the Raven, and is relatively indeed in this region much wider tlian in any 

 other Corvidae ; furthermore, the scar for the insertion of the snpra-s})inatus is 

 deejier. 



