. The American diceratheres. Rhinoceroses, Fossil; Paleontology. 2 3 Fig. 2. Diceratherium minutum (Cuvier). M^ X i. After Cuvier. Fig. 3. Diceratherium douvillei. M^ X i- After Osborn. than D. annectens of the same deposit (Compare PI. LVII with text-figure 11, also with PL LXIII, fig. 6, and PI. LXVI, fig. 1). In the latter form we naturally might expect to meet with a greater range of anatomical variations, especially in connection with the dentition. We may reasonably expect to find grinding teeth, having crests ranging from those which are quite plain to those which have the various incip
. The American diceratheres. Rhinoceroses, Fossil; Paleontology. 2 3 Fig. 2. Diceratherium minutum (Cuvier). M^ X i. After Cuvier. Fig. 3. Diceratherium douvillei. M^ X i- After Osborn. than D. annectens of the same deposit (Compare PI. LVII with text-figure 11, also with PL LXIII, fig. 6, and PI. LXVI, fig. 1). In the latter form we naturally might expect to meet with a greater range of anatomical variations, especially in connection with the dentition. We may reasonably expect to find grinding teeth, having crests ranging from those which are quite plain to those which have the various incipient projections, as crista, crochet, anti-crochet, etc. It is far from my mind to depreciate some, or all, of these characters; on the contrary, indeed, it is reasonable to expect that the dentition should be one of the first parts of the organism to undergo modification with a change in the environment. It is never- theless questionable whether the absence or presence of a crista, a crochet, and anti-crochet, more or less developed, or of a cingulum of greater or less prominence, should constitute a valid specific character in Diceratherium. I very much doubt whether these characters are of sufficient constancy to be relied upon to establish specific distinctions in a large collection of individuals from a given locality. Stress has in times past been laid upon the development of branches or spurs of different lobes of the cheek-teeth. It is plainly evident that D. annectens, as the result of its mode of life, was already in the time of the John Day more advanced, having filled out the grinding surface of its teeth more than its contemporary, D. armatum. In animals representing a later development in geological time, we should expect to find similar evidence of progression, and in a large assemblage of individuals that not all the specimens, say of D. cooki for example, are provided with crista and crochet united on the premolars and with crista small and crochet larger on th
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