158 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
The lunar is very massive and larger than the scaphoid in almost 
every dimension, articulating with the latter only by a narrow band near 
the proximal end, a facet which is moderately concave in the dorso- 
palmar direction. The radial surface is in two connected portions, a 
broad anterior area, which is strongly convex palmo-dorsally and is 
reflected far over upon the dorsal face, and a very much narrower, 
oblique and somewhat concave posterior portion ; the palmar face is very 
low proximo-distally, very broad and much roughened. On the ulnar 
side there is no facet for the pyramidal, except a very small one at the 
palmo-distal angle ; dorsally there is no contact between the two carpals. 
Bistally, the almost equal facets for the magnum and unciform meet at 
an acute angle and form a sharp, ridge-like portion between the two 
carpals last mentioned. However, this ridge-shaped portion is confined 
to the dorsal moiety of the lunar and the facet for the magnum is in two 
quite distinct parts, though there is no break in the continuity of the 
articular surface ; the dorsal portion, which is on the wedge-like projec- 
tion, is convex and obliquely lateral, rather than distal in position, while 
the palmar portion presents distally and is concave. Much the same 
description may be given of the facet for the unciform, except that the 
dorsal is more concave and distal and the palmar portion is considerably 
narrower than the corresponding part for the magnum and is more 
oblique, less completely distal. 
In Toxodon the lunar differs in a number of particulars from that of 
Nesodon. The radial surface has a more decidedly convex anterior por- 
tion, which is reflected farther down upon the dorsal face, while the pal- 
mar portion is very much reduced in size. On the ulnar side, the lunar 
has a distinct contact with the pyramidal, a contact which is both dorsal 
and palmar, and on the distal end the faces for the magnum and un- 
ciform meet at a much more obtuse angle and, even dorsally, these facets 
are much more distal than lateral, so that there is hardly any ridge-like 
prolongation. 
The pyramidal is broad transversely and very low proximo-distally. 
On the dorsal face, near the radial border, is a prominent tubercle for 
ligamentous attachment. The articular surface for the ulna is large, 
transversely oval and deeply concave, and on the palmar side is quite an 
extensive facet for the pisiform, of irregularly semicircular shape. The 
distal end is covered by the large, somewhat saddle-shaped facet for the 
