454 HARRIS HAWTHORNE WILDER ON 
the capitulum of the radius fit respectively into its dorsal and ventral continuations 
during forced extension and flexion of the forearm. These slight grooves or depressions, 
of which the ventral is, perhaps, a little stronger than the dorsal, are thus the first sugges- 
tions of the olecranar and cubital fossae which develop in higher forms. 
The humerus is distinguished from the femur by its sharp crista ventralis which pro- . 
jects farther than that of the femur and is differently shaped. This same feature, which 
marks the ventral side, and the large and spherical external condyle serve to orient the 
humerus. 
Femur.— The general shape of the femur is like that of the humerus, but without 
much flattening at the proximal end. Here it shows two projections for muscular attach- 
ment: (1) a distinct process, mostly formed by bone, but tipped with a cartilage which in 
the adult is independent of the main epiphysis, and (2) a ridge or crest upon the side of 
the head, involving also a part of the shaft. It is somewhat difficult to compare these two 
distinct features with the single crista ventralis of the humerus, but in accordance with 
position it would seem that the bony process corresponds most closely with that part, and 
may thus bear the same name, while the ridge which lies more upon the external lateral 
aspect may be designated as the crista lateralis. As this crest is similar in appearance, 
though not in position, to the proximal cartilaginous part of the crista ventralis of the 
humerus, it is possible that these two parts found in the femur correspond to the single 
process of the humerus, and that in the former a difference in motion and consequently 
in muscular insertion has separated the two parts and diverted one of them from its origi- 
nal position. Such an explanation is, however, not in accord with the almost universally 
greater differentiation of the anterior limb, and one would expect to find in the femur 
the more primitive condition. Hoffmann distinguishes in the Urodeles a single projec- 
tion referred to as crista femoris, a name applied by Gaupp to a similar part in the frog, 
but the femur of this latter animal is so unlike that of Necturus that homologies of parts 
are uncertain. It hence seems better to refer to the two processes found in Necturus by 
the two terms given above, crista ventralis and crista lateralis, terms which accurately 
express the position of the parts, and one of which suggests a justifiable homology with 
the humerus of the same animal. 
The distal joimt is imperfectly divisible into the external and internal condyles, 
although there is no distinct groove between them. The internal condyle is larger and 
longer and serves as the main point of origin for both flexor and extensor muscles of the 
lower leg and foot. The smaller external condyle articulates with the proximal end of 
the fibula. 
The osseous crista ventralis, separated from the head by a notch, is sufficient to dis- 
tinguish femur from humerus and to mark the ventral side of the bone. This and the 
more projecting internal condyle of the distal epiphysis will complete the determination. 
