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PROCEEDINGS OF THE NATIONAL MUSEUM. 
were also hollow, and probably filled Avith marrow. In the pe^nguins 
the leg bones are lilled with cancellar tissue. 
The l)ird to which this humerus l)elonged was more highl}" special- 
ized, more completely adapted for subaquatic flight, than the Great 
Auk, although the wings were not so extremely modified as those of 
the penguins. This is probably due to the fact that the penguins swim 
solely with their wings, while the auks use both wings and feet. The 
occurrence of a flightless auk at so low a geological liorizon as the Mio- 
cene is of great interest, as indicating a much earlier origin for the 
family. From the greater degree of specialization of the wings, it is 
Pigs. 1 and 2.— Superior and infeeior views of type specimen of Mancalla californiensis. 
Fig. 3.— Corresponding portion of left humerus of Lomvia troile californica, all slightly 
enlarged. 
fair to infer that the bod}" of Mancalla was larger in proportion to the 
size of the humerus than that of the Great Auk, and that hence the 
actual bulk of the two was not greatly dissimilar. Mancalla was cer- 
tainl}^ larger than any of the murres, although its nearest living rela- 
tive appears to be the Pacific Murre, Lomvia troile californica. 
In small birds absence of the power of flight implies freedom from 
enemies, and as this practically means isolation, it is probable that this 
flightless auk bred on some islands near the coast. The mollusk fauna 
associated with the specimen is Miocene in its aspect, and also indicates 
a cooler climate than that now prevailing in the latitude of Los 
Angeles, approxmiately that of Puget Sound, 
t\ 
