542

34

phaps. The calcaneal canal is smaller. The tendinal groove (fig.1, u) is shallower.
The ectocalcaneal process (s) is narrower : the groove on the outer side of that process
is also narrower, and is defined by a ridge not developed in Didus. The short ridge or
process below the posterior margin of the entocondylar cavity in Didus (fig. 10, j) is
more developed ; it is feebly indicated in Pezophaps, and is continued into the ento-
gastrocnemial ridge (fig. 4, g), which is not the case in Didus. Didus has not the
entometatarsal ridge (fig. 4, e) anterior to the entogastrocnemial ridge (ib. g), but only
the latter, which is strongly marked and more internal in position (fig. 16,g).

The postinernal depression (fig.2, v) receiving the larger of the two upper inter-
osscal canals (l) is narrower, and in Pezophaps minor deeper, than in Didus, owing to the
more posterior position, in Pezophaps, of the entogastrocnemial depression (i) defining that
depression internally. The antero-superior interosseal depression (i) is deeper in Pezo-
phaps than in Didus ; but the insertional surface for the tibialis anticus (fig. 14, n) is
better-defined in Didus. The anterior ectometatarsal ridge (fig. 1, k) is more strongly
marked in Pezophaps than in Didus.

The groove leading to the lower interosseal canal is more strongly marked in Didus
(fig. 15, p) than in Pezophaps (fig. 3, p), and indicates a more powerful "adductor
muscle", the tendon of which emerges at the interspace between the neck of the middle
and outer trochleae, in its course to be inserted into the outer toe.

The middle trochlea (III), as compared with the outer (IV) and inner (II) trocheae, is
larger than in Pezophaps (fig. 3) than in Didus (fig. 15) ; its relative position to the outer and
inner trochleae, and the consequent curve which they describe transversely, I find, in the
specimens before me, to be the same in both extinct genera.

In order to facilitate future comparisons and the following of the above descriptions,
I subjoin the names of the parts and their symbols in Pl. III. which appeared to me
to call for special notice in this part of the osteology of Didus and Pezophaps.

Parts of Metatarsus.

marked marked
Entocondylar cavity .................. a Ectinterosseal canal ...................... m
Ectocondylar cavity ................... b Facet for "tibialis-anticus" tendon ... n
Intercondylar process ................... c Anterosseal ridges .......................... o
Intercondylar triangular tract ........ d Lower ninterosseal or "adductor"
Entometatarsal ridge ..................... e canal, anterior orifice .................... p
Entocondylar ridge ....................... f Lower interosseal or "adductor"
Entogastrocnemial ridge ............... g canal, posterior orifice ................. p'
Entocondylar tuberosity ................ h Adductor bridge ............................ q
Antinterosseal depression ............. i Entocalcaneal process ................... r
Ectometatarsal ridge ..................... k Ectocalcaneal process ................... s
Entintersosseal canal .................... l Calcaneal canal ............................. t