0. C. Marsh on Oretaceous and Tertiary Birds. 207 
and a faint indication of its continuation can be traced nearly 
to the ecto-condyloid surface, where it passes into a small, acute, 
elongated tubercle, which is just outside of the triangular prom- 
in its inner margin a small elongated foramen, leading obliquely 
downward and inward. 
The portion of the shaft preserved is robust, and somewhat 
flattened in an antero-posterior direction. In the lower fourth 
of the bone, the transverse diameter gradually increases, an l 
reaches its maximum at the extremity of the distal condyles. 
The shaft curves forward slightly just where it begins to expand 
above the lower condyles, closely resembling in this respect the 
tibia of the turkey ; and it has at this point little of the marked 
Inward curvature. characteristic of the swimming birds, but is 
So straight, that its median plane, if continued, would divide 
the trochlear surface nearly equally. . 
The dimensions of the specimen are as follows :— 
of portion prese : 70 
Width of condyles in front, ‘ 23 
Depth of outer condyle, . : 19°1 
Width of bridge at center, . ° : 52 
‘ransverse diameter of upper outlet, ; er 
Transverse diameter of lower outlet, . ‘ 4°4 
Transverse diameter of shaft where broken, . —-‘11°8 
Antero-posterior diameter of shaft where brok 9°6 
A consideration of the characteristic points of this interesting 
fossil leads to the conclusion that it should be placed in the 
order Natatores, but additional remains will probably be 
Tequired to determine its exact affinities. It shows a strong 
resemblance in several respects to the Lamellirostres, and also to 
the Longipennes, but differs essentially from the typical forms 
of both these groups. For the extinct genus evidently <a 
sented by this specimen the name Laorn’s* is proposed. ' 
* Adoc, stone, and "Oprtc, bird. 
