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Show 712 DR. E. LONNBERG ON THE [June 19, sharpness, stoutness, and prominence of the three principal costae on their outer surface, aud tbe small development of the two secondary ones." This is quite right, but it cannot be regarded as proving any close ovine affinity, as it is a primitive feature shared by a large number of Antelopes. In the next line (I. c.) Dawkins asserts of the upper true molars, as some authors (Bichardson, I. c. p. 71 &c.) have done before him : " O n the internal aspect there is no accessory column ; " and he lays much weight on this. About five years earlier, however, the keen observer Biitimeyer had (I.e. p. 91 footnote) stated the normal presence of such accessory columns, although they are small. On the material 1 have received from the Nathorst Expedition to East Greenland, 1 am able to verify Biitimeyer's observations (fig. 7). These facts, in addition to the above statement concerning the milk-teeth, indicate that there is a remarkable difference in this respect between tbe dentition of the Musk-ox and that of the Sheep, instead of the presumed likeness. The " small accessory valley at the inner interspace between the two principal ones," as it is described by Dawkins (I. c. p. 8), is present in the upper true molars of Ovibos, which in this respect resembles Bovidce, as that author has stated. The same valley is also found in Nemorhcedus, Rupicapra, and in Bubaline, Hippotraginel, and Tragelaphine2 Antelopes, but not in Antilope, Gazella, &c. In Sheep and Goats this " accessory valley" seems to be less constantly developed. Ovibos differs therefore with regard to its molars more from the Caprina and Antilopina than from the Bupicaprina. Bubalidina, Hippotragina, and Bovina. With tbe first mentioned of these latter groups it has the " accessory valley " in common, and with the others also the accessory column. The question now is to decide how much can be regarded as parallel and how much as affinity. This decision is again dependent upon what may be the origin of the accessory column. Butimeyer seems inclined to make a sharp difference between accessory columns and basal tubercles 3. The former he thinks are derived from the isolated inner column of the Anoplo-therium tooth ; the latter are " blosse Ausbildungen des unter Hufthieren so allgemein verbreiteten Basahvulstes." As "accessory columns" he counts only those between the two main lobes of the inner side of the upper molars ; but as " basal tubercles " are regarded not only accessory elements found at other places on the upper molars, but also all accessory tubercles and columns on the mandibular molars, even if they look exactly like the accessory columns, recognized elements of the upper molars and just as much developed. Such a division seems, however, less easy to carry out in a quite satisfactory manner. At the same time that Butimeyer calls the accessory elements of the mandibular molars in Bos basal tubercles, he admits himself that a basal tubercle can be developed to something in shape and structure absolutely like an accessory 1 Cf. Riitimeyer, Gesch. d. Rind. tab. i. fig. 11. 2 Cf. Flower and Lydekker: ' Mammals, living and extinct' 3 Gesch. d, Rind..pp. 78-79. |