570 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
in the formation of the zygoma, which often affords, especially by its anterior 
connections with maxillary or lachrymal, or both, valuable indications of 
affinity among Redents, remains unknown. I can discern no trace of the 
sutures. I conjecture, however, from the line of fracture of an accidentally 
broken specimen, that the malar is anteriorly wedged hetween two (anterior 
and posterior) zygomatic processes of the maxillary, and extends nearly or 
quite up to the lachrymal,—a supposition strengthened by the observed state 
of the parts in Cynomys and Arctomys, for example. Similarly, I am of 
opinion that posteriorly the end of the malar will be found to represent the’ 
prominent angle or corner of the zygomatic,arch, being splinted underneath 
a horizontal forward spur of the squamosal. The malar helps to define the 
brim of the bony orbit by a small projection from its upper edge near the 
fore end; this is better marked in younger skulls, being obsolete or nearly so 
in very old ones. With only aged skulls before him, Baird recognized a 
lachrymal in a tubercle at the fore upper corner of the orbit; in a younger 
specimen, I see nearly the whole contour of a large lachrymal, lying mostly 
within the orbit, as a thin scale, thickening only at the edge to form the 
nodule just mentioned; it has a conspicuous canal. The suture of the 
palatal plates of the maxillaries and palatines will probably be found opposite 
the interspace between the last and penultimate molars. Anteriorly, the 
maxillo-premaxillary and fronto-maxillary sutures are preserved in one speci- 
men; the former encircling the rostrum below and laterally, then trending 
obliquely backward as it mounts toward the forehead; the latter being a short 
backward-outward suture opposite the site of the lachrymal. Owing to the 
narrowness of the nasals posteriorly, the premaxillaries gain the top of the 
skull in a considerable area; their suture with the frontal is a straight trans- 
verse line continuous with the similar naso-frontal suture. Thus the frontal 
bone ends squarely in a straight line across the forehead, with prominent lateral 
angles formed by the fronto-maxillary sutures. The nasals, like the pre- 
maxillaries, are perfectly distinct all around; their shape has been already 
noted. For the rest, the auditory bullae -are the only other bones whose 
whole periphery can be observed in the specimens before me; their remarkable 
tubular prolongation from a globular base has been sufficiently described 
above. 
Vertebral column.—Formula:—C. 7; D. 138; L. 6; 8.5; Cd. 11=42 
vertebre. In life, in a usual position, the backbone from atlas to end of 
