simple. | labial re-entrant | fold; occlusal | fold; anteroconid | pattern complex. | large; occlusal | | pattern moderately | | complex. | | | | | m3--Three wide lingual | Three moderately | Narrow lingual re-entrant folds | narrow lingual | re-entrant of near equal | re-entrant folds | folds variable in length; antero- | of unequal length, | number, as many as 3; conid absent; | 1st and 2d long, 3d | anteroconid present; occlusal pattern | short; anteroconid | occlusal pattern simple; 1 labial | absent; occlusal | complex; 2 labial re-entrant fold. | pattern moderately | re-entrant folds. | complex; 1 labial | | re-entrant fold. | -----------------------+-----------------------+------------------------ [Illustration: FIGS. 22-31. Dorsal and lateral views of the bacula of the Recent genera (and species of the genus _Zapus_) of the subfamily Zapodinae. × 10. FIGS. 22 and 27. _Eozapus setchuanus_ (after Vinogradov, 1925:585). FIGS. 23 and 28. _Zapus t. trinotatus_, adult, No. 94596 MVZ, 1-1/4 mi. ENE Amboy, 350 ft., Clark County, Washington. FIGS. 24 and 29. _Zapus p. princeps_, adult, No. 20870 KU, 3 mi. S Ward, Boulder County, Colorado. FIGS. 25 and 30. _Zapus h. pallidus_, adult, No. 22954 KU, 4 mi. N, 1-3/4 mi. E Lawrence, Douglas County, Kansas. FIGS. 26 and 31. _Napaeozapus i. insignis_, adult, No. 41110 KU, Shutsburg Rd., at Roaring Creek, 600 ft., Franklin County, Massachusetts.] EAR OSSICLES.--The auditory ossicles are of three types which differ only slightly. These ossicles possibly are more conservative than some other structures because the ossicles are not so much affected by the molding influence of the environment. Instances of variation in the auditory region in mammals in general are small, even at the family level; therefore, these differences in the subfamily Zapodinae are offered as additional support for recognizing _Eozapus_, _Zapus_, and _Napaeozapus_ as distinct genera. The distinctive features are chiefly in the malleus and incus; the stapes, however, differs slightly and, therefore, it too is described (see figs. 32-34).