Robert J. Russell

“ In every example of P. bulleri that I have seen (more than 100 specimens, representing all of the named subspecies) the anterior palatine foramina are long and slitlike and the nasals are always narrow and emarginate posteriorly, whereas in P. alcorni the anterior palatine foramina are short and round and the nasals broad and squarely truncate posteriorly. ”

“ In P. alcorni the enamel present is thick, but it occurs only on the inner one-fourth of the posterior wall of the tooth. The enamel is always complete in P. bulleri; but in some old individuals it becomes thin with wear, and at a casual glance may appear to be partly or entirely absent. Close examination under magnification reveals, however, in every specimen of P. bulleri, a fine line of enamel completely across the posterior wall. It seems that the posterior enamel plate of M1 is disappearing in both P. bulleri and P. alcorni. ”

“ Among the Pappogeomys collected by Alcorn were three specimens from the high Sierra del Tigre, an isolated range not previously sampled for pocket gophers. The Sierra del Tigre is situated in southern Jalisco and western Michoacán, and, like most of the mountainous terrain in this region of México, is volcanic in origin. To the south the Sierra del Tigre descends abruptly to lower elevations of the arid coastal plains, uninhabited by gophers of this genus. ”