THE FOSSIL AVIFAUNA OF THE 
307 
^'Echnop hones occidentalis (Lawr.) 
Colymbus holbcelli (Reiiih.) 
Colymbus auritus Linn (?) 
Colymbus nigricollis californicus (Ileerm.) 
Podilymbus podiceps (Linn.) 
LONGIPENNES. 
Apparently there was a complete absence of tlie Alcida or any fcjnns especially 
like them, but this was not the case with the Gulls and Terns for there are numer- 
ous bones to testify to their presence. 
Unfortunately, skulls of Gulls or Terns are entirely missing from this fo.ssil 
material, nor did I find any vertebra; that could Avith certainty Ije said to Ixdong to 
any larine forms. On the other hand several patterns of the liuinerus were col- 
lected, ranging from those of very small size to one of a large Gull. There aiv four 
distinct kinds of coracoids, also varying greatly in size, and there are Auirious tai’so- 
metatarsi, carpo-metacarpi, a finger joint of a Gull, a feAV tibia', but nothing more. 
There is a distal two-thirds of a right humerus that is identical in size, form 
and character with the corresponding bone in the skeleton of Larus argentatus (No. 
18,167, Coll. U. S. Nat. Mus.), and it undoubtc'dly belonged to an individual of the 
species noAV knoAvn as Lams argentatus smithsoniamis It is not repiescMited 
by any other bones. 
Next I find a perfect coracoid of a Gull, considerably .smaller than the coracoid 
in L. argentatus smithsonianus, but only a trifle .smaller than the Ijone as it (K'curs 
m Larus glaeicus, with AAdiich it agrees almost exactly in character. It is the cora- 
coid of the left side. There is also the distal moiety of a left ulna of a Gull appar- 
ently of the same size, as it differs in the same proportion Avith the ulna of Larus 
glaucus, with AAdiich it otherAvise agrees. I am of the opinion that it kloiigmd to 
the same species, though perhaps not to the same individual. Two large tibio-tarsi <if 
Gulls are also found,— one lacking the proximal extremity, and one the pn»ximal 
moiety. These are stouter than the tibio-tarsi in Larus glaucus but Avere not (piite 
as long. Possibly they may have belonged to the same species, Avhich may have 
had stouter iiehdc limbs than Lams glaucus although not quite .‘»o large a binl. As 
this fossil coracoid belonged to a Gull considerably larger than Icarus a. smifhson- 
ianus, it could hardly have belonged to Larus occidentalis, of Avhich species unfor- 
tunately I haAm no skeleton, but it is about the size, judging from external mea.Muv- 
ments, of L. a. smithsonianus, and probably has a skeleton of nearly similar proiMU- 
tions. The coracoid is too small to have belonged to a Larus marinus, and at any 
rate it is not at all likely that it was that form. Moreover it Imlonged to a larger 
bird than Larus cachinnans, a species no larger than the common 1 lerring Gull. 
Indeed I mu,st believe that there Avas a large Gull present in the fonner avi- 
fauna of the Silver Lake Region, during later tertiary times, which has since become 
extinct. It Avas somcAvhat smaller than Larus glaucus, and if the tibio-tarsi, 
described above, belonged to the same species, it had stouter and shorter legs. 
