488 
THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 
only noteworthy difference being that the second phalanx is distinctly narrower 
and more slender. In spite of their very elongate proximal phalanges, the lateral 
digits cannot have reached the ground, and must have formed mere dew-claws the 
unguals extending only to the lower end of the proximal phalanges of the median 
digits. This shortening affects principally the metatarsals. 
Filhol’s drawing of the phalanges of the lateral digits oi A. velaunus (PI. 25, 
fig. 124) shows them to have been different from those here described. The proxi- 
mal one is much shorter and heavier, the second more slender, and the ungual much 
smaller and more pointed. The relative lengths of the median and lateral digits are 
about the same in both species, but in A. velaunus the lateral metatarsals are much 
longer and the phalanges shorter, while in the American form these proportions 
are reversed. 
In the median digits the proximal phalanx does not exceed those of the lateral 
digits in length, but is very much larger in every other dimension, and especially in 
breadth. The general shape is not unlike that found in Or eodon, but the bone is 
straighter, broader, less arched, less compressed antero-posteriorly, and the distal 
trochlea, is less deeply notched in the median line. The phalanx is broadest and 
deepest at the proximal end, and the articular surface is a shallow concavity, notched 
on the plantar border for the keel of the metatarsal. The lateral processes for 
ligamentous attachments just above the distal trochlea are better marked and more 
prominent than in Oreodon, and the pits are correspondingly deeper. 
The second phalanx is asymmetrical, though those of the two median digits 
form together a nearly symmetrical pair; not entirely so, however, for the two are 
not quite alike. This phalanx is shaped like the corresponding one of the lateral 
digits, but is much larger and heavier. The proximal trochlea is very obscurely 
divided into two facets, and the distal trochlea is oblique, inclining toward the 
median line, as it passes dorsally ; it is reflected distinctly farther upon the dorsal 
side of the bone in the fourth digit than in the third. 
The ungual phalanx is much like that found in Oreodon, but is relatively 
broader, more regularly arched on the dorsal surface, more depressed, of less dorso- 
plantar diameter, and more bluntly rounded distal end. In spite of these differ- 
ences, the unguals of the two genera are manifestly of the same type, a fact which is 
not without morphological significance, because this type is not at all a common one. 
The phalanges of the median digits in the European species, according to 
Kowalevsky and Filhol, are m many respects quite different from those here described 
an referred to A. brachyrhynchits. The proximal one is more slender and tapering, 
as well as longer iri proportion to the metatarsals. The second is much less mas- 
the ’.mini ' compressed, and pointed. In fact, 
S JZt are more like those of Dtplopru than those of 
