1028 MK. W, p. PYCRAFT ON TEE [Dec. 19^ 



form of the coronoid. This is long, naiTow, and pointed. Its 

 anterior half remains distinct throughout life, the posterior region 

 fuses with the angulare. The dentary suture also remains distinct. 



In the Divers the supra-angular is pierced by a large foramen, 

 which remains permanently open ; furthermore the jaw may be- 

 distinguished from that of the Grebes by a deep notch situated 

 immediately behind the outer border of the glenoid surface for the 

 external condyle of the quadrate ; in this last it agrees with many 

 Alcidse. The internal angular process is feebly deyeloped. 



The mandible of the Podicipides (Grrebes) lacks the notch just 

 described, and the foramen piercing the supra-angular is much 

 reduced in size, and shut off from within by the base of the 

 coronoid ; the internal angular process is moderately well 

 developed. 



TJie Hyoid. 



The Jiyoid of the Pygopodes di:ffers markedly from that of the 

 Alcidse, both in the form of the basihyal and basibranchial 

 ossifications, neither do they bear any close resemblance either to 

 those of the Tubinares or of the Impennes, In each of the three 

 last-mentioned groups the first and second basibranchials are 

 anchylosed, the latter being continued backwards in the form of a 

 median pointed bony style between the ceratobranchials to form 

 the " urohyal." In the Pygopodes the first and second basi- 

 branchials appear to remain distinct throughout life. 



In the Pygopodes the first basibranchial — the main body of the 

 bone — takes the form of an oblong plate hollowed dorsally, and 

 with a slight median keel ventrally. The basihyal is partly 

 ossified, the ceratobranchials are relatively very long, the epi- 

 branchials short and slender. 



In the Colymbi the first basibranchial takes the form of a 

 flattened oval, and the anterior region of the ventral median keel 

 is strongly developed. The second ("urohyal") is apparently but 

 imperfectly ossified, only the very centre of the rod-shaped style 

 being bony. In the Museum skeletons there is no basihyal 

 ossification, but this may have been lost in maceration. 



iii. The Skull op the JSTESTLiifG. 



Por the nestling which forms the subject of the following notes 

 I have to thank the Hon. Walter Rothschild, who kindly provided 

 it specially for this purpose. 



a. Cartilage-hones. 



The hasioccipital seen externally is linguiform ; it forms the 

 central portion of the occipital condyle posteriorly, and anieriorly 

 is underflooi'ed by the basitemporal plate of the parasphenoid. 

 It joins the exoccipital by harmony suture. Internally it is 

 bounded laterally by the exoccipital and anteriorly by the basi- 

 sphenoid. 



