1895.] HTOID BO]S^E OF CEETAIIf PARROTS. 167 



calling to mind the " hypocleidium " (h). Each crus of the arch 

 has a slight sigmoid flexure as it advances from its base, the 

 first flexure convex dorsad and the more distal one convex veutrad. 

 The symphysis, as seen above, narrows somewhat towards its apex 

 (which is blunt) and is slightly convex transversely on its dorsal 

 side and flattened beneath or even slightly concave transversely. 

 The symphysis is about as broad as the two crura combined, and 

 each crus continues of nearly the same breadth till it closely 

 approaches the symphysis. 



The urolujal is relatively as well as absolutely much shorter than 

 in P. erithacus and more laterally compressed. It also bends 

 decidedly ventrad towards its apex, which is more truncated. 



'J'he entofjlosmm has each of its lateral elements more laterally 

 compressed than in P. erithacus, so that when seen above it 

 appears much more slender, especially towards its antero-posterior 

 middle. Towards its anterior end it expands transversely to a 

 considerable extent, the expansion looking upwards and inwards 

 dorsally, and downwards and outwards ventrally. Each terminal 

 expansion develops three minute ])rocessea from its anterior 

 margin, whereof two very slightly marked ones are directed for- 

 wards and one inwards to nearly meet its fellow of the opposite 

 side, a small piece of cartilage completing their junction and that 

 of the anterior ends of the two entoglossals, but for which there 

 would be a conspicuous median notch at the front end of the 

 entoglossum. This whole anterior part constitutes a structure 

 very concave dorsad and convex ventrad. The hinder end of each 

 entoglossal also expands and meets its fellow of the opposite side, 

 the space thus enclosed by the two entoglossals being longer and 

 narrower relatively than in P. erithacus. 



The posterior extension of each entoglossal is slightly longer 

 relatively and more pointed than in P. erithacus. The dorsal 

 surface is slightly convex in both directions, though the two 

 entoglossals incline ventrad to their posterior junction, so that the 

 whole entoglossum is dorsally deeply concave transversely in front 

 of its junction with the basihyal. 



When the entoglossum is viewed laterally, its anterior end is 

 seen to be vertically expanded and with a slightly rounded anterior 

 margin. Backwards from this vertically expanded anterior portion, 

 the entoglossal contracts dorso-ventrally rather suddenly and then 

 slightly expands postaxiad with a rather convex dorsal margin 

 and a strongly concave ventral one. This concavity is produced 

 by the projection ventrad of a strongly marked process which may 

 be distinguished as the anterior lateral process, of which there is but 

 a rudiment in P. erithacus. Behind this another, larger process, 

 which may be named the posterior lateral process, projects more 

 ventrad still, there being, of course, a strong concavity, or notch, 

 between these two processes. This posterior lateral process consists, 

 as in P. erithacus, of that ventral portion of the entoglossum which 

 goes to join its fellow of the opposite side and form the bony isthmus 

 in front of the articulation of the entoglossum with the saddle- 



