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Show I . I ADDENDUM A. THE CRANIAL AND DENTAL CHARACTERS OF GEOMYID..E. [Reprinted, with some modification, fi·om the Bulletin of the United States Geological and Geographical Survey of the Territories, 2d series, No. 2, pp. 81-90, published May 11, 1875.] I 1-1 0-0 4-4 5-5 10 ·1-1; 0·u-O; M.4-4; =5-5= 10 = 20· In its massiveness and angularity, the skull of the Geomyidte differs altogether from that of the Saccomyida, in which the cranium is singularly papery and bullous, with few angles; and it quite closely resembles an arvicoline type. The jaws are remarkably strong; the incisors immense; the zygomata Haring; the occipital region is extensive; the palate proper is contracted and at the same time prolonged downward; there is a long arched interval between molars and incisors. On a plane surface, the skull without the lower jaw rests level upon the molars and incisors; no other points touching the support . The molars are all rootless and perennial. The inferior incisors traverse the whole jaw. The superior incisors are semicircular. No anteorbital foramen occupies a usual site. The complex temporal bone is inordinately enlarged in all its elements, but especially the squamosal, which represents most of the cerebral roofing at ~Xl)cnse of the reduced pnrietals. The malar is merely a short splint; there is an osseous tubular meatus auditorius. There are no orbital processes; the interorbital constriction is narrower than the rostrum ; the latter is more than a third of the length of the whole skull: Such are some of the general features, from which we may proceed to details-first of configuration of the whole, afterward of characters of individual bones. Viewed from above, rather less than the posterior two-thirds of the skull presents a subquadrilateral figure, from which the rostrum protrudes in front. The greatest width is opposite the fore pnrt of the zygomata h most ~tt.s~s |