528 THE OSTEOLOGY OF HYvENODON. 
.j;s; 
un.l abuts aguinst the ectocuneifbnn. for which it has a facet. The proximal por 
tion of the shaft is laterally compressed, but of considerable thickness antero-poste- 
riorly ; it soon becomes slender and subcylindrical. The distal trochlea is narrow, 
of asymmetrical shape, with prominent carina. xx, i, j r- 
Owing to the small proximo-distal diameter of the mesocuneiform, the head of 
nit. II rises to a considerably higher level than those of mt. I and mt. HI, and is 
wedged in firmly between the ento- and ectocuneiforms, with the latter one of which 
it has an extensive articulation. On the fibular side the head is excavated to re- 
ceive that of lut.lll. The shaft at first pursues an oblique course, its proximal 
|)ortion being inclined outward as well as upward, but then turns and most of the 
shaft runs more nearly parallel with those of the other digits. Something of the 
same sort may be observed in Lutra, but the curvature of the proximal end is less 
ill amount and in the opposite direction. In HycBnodon the shaft of mt. II is weak, 
slender and relatively short ; the distal end is but moderately expanded and thick- 
ened ; the trochlea is asymmetrical and somewhat obliquely placed. 
'File third metatarsal is the longest of the series and, except mt. IV, the heaviest. 
The head is narrow and convex from before backward, terminating on the plantar 
side in a rough knob, which is especially large and rugose in H. horridus. On the 
fibular side of the head is a deep cavity into which is received a rounded articular 
projection from the head of mt. IV. A second concave facet for mt. IV extends 
posteriorly to the end of the plantar knob already mentioned. Mt. Ill and IV arc 
thus very firmly interlocked, while the connection of the former with mt. II is looser. 
The shaft is slender, nearly straight and of trihedral section, the apex of the tri- 
angle being tlie plantar edge. The distal end is more expanded than in mt. II and 
the trochlea is wider and more symmetrical, with the carina nearly in the median 
line. The lateral ligamentous processes above the trochlea are quite prominent. 
The fourth metatarsal is somewhat shorter and slightly stouter than the third, 
but otherwise similar to it. It is closely interlocked with both the adjacent meta- 
tarsals, having on the head a deeply concave facet for mt. V and a prominent articu- 
lar convexity for mt. III. I he heads of these three metatarsals stand at nearly the 
same level, each of them articulating with a single tarsal element. The shaft and 
trochlea ol' mt. IV are very much the same as those of mt. Ill, with which it forms- 
an almost symmetrical pair. 
Tlie liftlimi.tiitarsal i.s considerably longer and heavier than the first; the head ' 
IS distingiiis heel by an inmsually large process for ligamentous attnchinent. which 
.appoars ,m the hbubir side. This proeess is much larger and more massive than in 
till side'nim ta.' ‘-“"i «- 
The //m/««g.,r„rthe pes differ little from those of the manns. They are only 
