1036 Mil. w. p. pychafx on the [Dec. 19, 



Podicipes Jiuviatilis, for instance, the width across the posterior 

 lateral processes may equal the whole length of the corpus sterni ; 

 in other words, the sternum may be as broad as long. In the 

 Divers the width across the widest part is about one-third the total 

 length of the sternum. There is no spina externa nor interna ; 

 instead, this region of the sternum is deeply hollowed. The lower 

 lip of the coracoid groove is very large, making the groove ex- 

 ceedingly deep. In the Diver this lip is not greatly developed. 

 The metasternum is deeply notched and not produced backwards 

 into a linguiform plate as in the Divers. The anterior lateral 

 processes are larger and project forward. In the Diver they are 

 sharply truncated, the free anterior border sloping distinctly 

 backwards. 



The comcojrf is short and straight, both in Grebes and Divers. 

 In the former, the epicoracoid is marked by a wide articular surface 

 running transversely across its ventral aspect. The procoracoid 

 process is absent. In the latter the broad articular surface is 

 absent on the ventral aspect and there is a small procoracoid 

 process. In both there is a well-marked processus lateralis. There 

 is no supracoracoid foramen, as in the Alcidae; the posterior free 

 border of the epicoracoid is almost knife-like and not, as in the 

 Alcidae, squarely truncate. 



The scapula, as compared with that of the Alcidae, is relatively 

 short, and has but a very narrow transverse articular surface, 

 instead of a very wide one as in Alcidae. In the Podicipides there 

 is a well-marked acromion process projecting downwards from the 

 shaft beyond the level of the coracoid articular surface. 



The clavicle is not provided with an external lateral facet for 

 articulation with the coracoid, as in many Steganopodes and 

 Alcidae. There is a small hypocleideum. The right and left 

 limbs of the clavicle are very broad and laterally compressed in the 

 Divers. In the Grebes the upper free end of each limb is pointed, 

 and runs along the antero-internal border of the scapula. 



vii. The Pelvic Giedle. 



The form of the pelvic girdle in the Pygopodes is unique amongst 

 living birds. Its most characteristic feature is the extraordinary 

 elongation and lateral compression which has taken place. 

 Although the synsacrum has been involved in this compression, it 

 is not, at first sight, so marked as in the innominate bones. The 

 preacetabular ilium is small and narrow, and widely separated from 

 its fellow of the opposite side, but is not otherwise very remark- 

 able. The postacetabular ilium, however, takes the form of a 

 broad, flat, almost or quite vertical lamina. This in the Grebe 

 meets its fellow of the opposite side, in the Diver is separated by 

 the knife-like ridge formed by the neural spines of the anchylosed 

 synsacral vertebrae. The ilio-ischiadic f orameu is moderately large ; 

 the obturator foramen in the Colymbi remains permanently iu 

 connection with the fissure of that name, in the Podicipides the 



