1899.] osTEOLosr oe the ptgopodes, 1037 



foramen is shut off from the fissure by a bar of bone. Tiie pubis 

 is long aud rod-shaped throughout in the Podicipides, but becomes 

 spatulate at its free end in the Coljmbi. There is no pectineal 

 process. 



The preacetabular ilium, the ischium, and pubis become more 

 or less completely ossified at a much earlier date than the post- 

 acetabular ilium. This last is as yet for the most part still 

 cartilaginous. The separate elements of the innominate bones 

 are still very distinct. 



viii. The Pecxohal Limb. 



The wings of the Grebe and Diver bear a very close similarity, 

 and perhaps more nearly resemble those of Fhalacrocorcuv than 

 of any other group. 



The wing of the Diver can be readily distinguished from that 

 of the Grebe by the great relative length of the metacarpals. 

 As Sbufeldt (18) has pointed out, the Divers in this particular 

 probably stand alone. The delto-pectoral crest is larger in the 

 Diver, and the fossa for the brachialis internus is deeper. There 

 is no ectepicondylar process nor subtrochanteric pneumatic fossa. 

 The delto-pectoral crest in the Divers is separated from the crista 

 inferior by a deep gorge — the planum intertuhercuJare ; this in the 

 Grebe is represented only by a shallow depression. The coraco- 

 humeral groove takes the form of a deep pit ventrad and distad of 

 the caput humeri. 



Tl\iQ forearm in the Grebe is nearly as long as the arm, consider- 

 ably less so in the Divers. 



In the manus the great length of the metacarpals in the Colymbi 

 has already been commented on; the Isb phalanx of digit II. in 

 the Divers is relatively shorter and broader than in the Grebes ; 

 the same applies to the remaining phalanges. 



The carpus does not seem to call for any special remark. For 

 further details concerning the fore limb, see Key (p. 1041:). 



ix. The Pelvic Limb. 



The pelvic limbs of the Grebe and Diver bear an exceedingly 

 close resemblance one to another, but differ in almost every 

 particular from those of any other group. 



T1\\Q femur is very short and thick, with a strong dorsal curve. 

 Its proximal and distal extremities are greatly elongated trans- 

 versely. The head lies rather below the level of the antetrochanter, 

 and bears a deep fossa for the ligamentum teres. The fibular 

 condyle is of great size, and lies con.siderably below the level of 

 the tibial. 



The tihio-tarsus is remarkable for the enormous development of 

 the cnemial crests, which form a large pyramidal process projecting 

 vertically upwards beyond the femoral articular surface. This 



Pboc. ZooL. Soc— i899, No. LXVII. 67 



