. The Deseado formation of Patagonia . Fig. 100. Upper and lower incisors, canines, and premolars- -1/2 natural size, after Ameghino. dentition. Unfortunately his type figure is from the sideand does not give all the desired information. In the upper dentition, the small incisors, pitted on thecrown, increase regularly in size toward the rear; and eachhas an external cingulum around the base. The canineis about twice the size of the adjacent incisor, and also has. Fig. loi. Milk incisors, canine, and premolars and permanent m. i—1/2natural size, after Ameghino. an external cingulum. The premol
. The Deseado formation of Patagonia . Fig. 100. Upper and lower incisors, canines, and premolars- -1/2 natural size, after Ameghino. dentition. Unfortunately his type figure is from the sideand does not give all the desired information. In the upper dentition, the small incisors, pitted on thecrown, increase regularly in size toward the rear; and eachhas an external cingulum around the base. The canineis about twice the size of the adjacent incisor, and also has. Fig. loi. Milk incisors, canine, and premolars and permanent m. i—1/2natural size, after Ameghino. an external cingulum. The premolars increase regularlyin size and also have at least an external cingulum. Figure101 shows a dentition which Ameghino described as themilk set of A. osborni. At the same time he remarks theunusual character of the deciduous canine in being two-cuspeil. I think this set of teeth should be interpreted asdeciduous inc. 2 to deciduous pm, 4, plus the permanent ASIMODEUS SCOTTI 141 molar i. With such an interpretation, we find the incisorsnormal, the canine normal though not as large as in thepermanent set, and the two-cusped tooth is the first milkpremolar. The last tooth in the series is considerablydifferent from the premolars and is evidently permanentmolar i, which is al)OUt the size and character of this toothin A. scotti, much too small to belong to A. osborni. Thisset of milk teeth differ from the permanent teeth in thatthe premolars do not have the a
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