HUMERUS FROM THE STONESFIELD SLATE. 459 
applies to the proximal end of the femur of the Hedgehog, which at 
first sight approximates in form to the fossil. 
The Bats probably make a nearer approach than the Insectivora, 
both trochanters being well developed; but in the Bat there is not 
the same concave channel extending down the shaft between the 
trochanters, which is so remarkable a character in the fossil. I am 
therefore disposed to believe that the Monotreme characters predo- 
minate, and justify us in believing that the specimen was impla- 
cental, although there may be some reason for believing that it was, 
to some extent, also marsupial in its characters. 
HuMERUvs. 
The right humerus rests flat in 
the matrix, so as to expose its pos- 
terior aspect. It is 1,4, inch long, Fig. 2.— Humerus. 
with a globose head, slender shaft, = 
straight on the anterior or inner 
side, concave on the external or 
posterior side, and compressed and 
somewhat expanded at the distal 
end. It is much more marsupial in 
its characters than the femur. ‘The 
head is ,°; inch wide, and is rather 
directed outward and backward ; it 
is about 5%; inch deep, and presents 
a form which is seen in Phascolarc- 
tos, but which is unusual. The 
shaft narrows to ;% inch in the 
middle, where its section would ap- 
parently be subtriangular, owing to 
the inner side of the bone being 
flattened vertically. This inner side 
extends upwards so as to form a 
small trochanter on the inner side 
of the articular head ; but the poste- 
rior border of the bone is sepa- _ 
rated from the head by a well-de- 
fined transverse depression. On the proximal half of the inner margin 
rises a well-defined moderately elevated crest, which, so far as I am 
aware, is not paralleled in position in any humerus which is com- 
parable with the fossil. The inner side of this ridge is continuous 
with the flattened inner side of the bone, and it extends up to merge 
in the trochanter; but the outer side of the ridge is defined by a 
slight clean groove. The ridge attains its greatest elevation at 5, 
inch below the articular head of the humerus, and nearly ;*, inch from 
its proximal articular surface. The distal end of the bone lies in the 
same plane with the proximalend. The external margin is expanded 
into a thin plate, which has a highly convex external outline. This 
plate on its posterior aspect is flat and smooth, and in no way de- 
fined from the rest of the bone. Its contour helps to form the bow- 
The outline shows the natural size 
of the bone. 
