noteworthy; though in its .general pattern it rK.sclv ai)i)rnach'.'s 

 what we find in the Urinatonda-. The pclM> in JiJtmoplioms 

 occidcntalis well exhibits all the characters ot this compound 

 bone among the podicipidine typos. In that sjjccics is much 

 elongated and compressed laterally, csi)ccially it> ])()S-acctahular 

 portion. In front of the acetabuLx the fused sacral crista rises 

 far above the fore part of the ihum on either hand.- - which 

 latter, each have the form of an oar-blade with a square!) 

 truncated anterior extremity. An extensive antitrochanter 

 surmounts either cotyloid cavity, while posteriorly the post- 

 acetabular surface faces almost directlv outwartls. Along the 

 dorsal middle Une, for the posterior third, of the ])elvis the iliac 

 borders are closely pressed together, marking the uro- sacral 

 vertebrae. Behind, a deep cleft indicates the di\ ision which 

 originally marked the terminal point of union between the ilium 

 and the very long and narrow ischium. The obturator foramen 

 completely merges with the obturator sixice, and the much- 

 extended, flat, ribbon-like post-pubic rod is widel\ seixuated 

 from the lower ischiac border, being carried far hack almost 

 opposite the pygostyle. The ends of these bones of the ])elvis, 

 however, are not dilated as are the postpubic l)ones in the 

 loons. The ischiac foramen is large, and of an elhptical out- 

 line. Podilymbus presents almost the same pelvic characters 

 as those just described for yEchmophorus. and in this species 

 the OS innominata fuse completely with the " sacrum," — though 

 posteriorly the superior iliac margins do not quite meet over the 

 uro-sacral vertebrae. 



The sternum is very characteristic. In Figures i, a and i, b 

 I have drawn it for Colymbus nio;ricollis calif onikns where its 

 podicipidine features may be seen, (ienerally speaking it is 

 broad and short, with a large subelliptical notch cutting out its 

 xiphoidal portion on either side of the keel. This gives rise to 

 a pair of flaring external xiphoidal processes, which curve out- 

 wards, then inwards, extending rather beyond the mid-xiphoidal 

 prolongation. They are long and narrow in the short-billed 

 grebes, and broader and relatively shorter in .■F:chm.)phorus and 

 Colymbus. The mid-xiphoidal process always shows a triangular 

 notch, which is much deeper in Podilymbus than in other species, 



