| OCR Text |
Show 714 DR. E. LONNBERG ON THE [June 19, Examples proving such a statement may be found in sufficient number, but I think that offered by the genus Cephalophus is among the best. About this genus Sclater and Thomas say in ' The Book of Antelopes' (p. 121): " Upper molar teeth short and broad; in the larger species with an additional column on the inner side; " and Butimeyer ' speaks of " Spuren von Basalsaiilchen." In the small species of Cephalophus accessory elements are more or less comparatively wanting. In a skull of C. melanorheus Gray, from the Cameroons, I failed to find any accessory elements except on the hindmost milk-premolar. In the skull of the medium-sized C. dorsalis Gray, subsp. castaneus O. Thomas, the accessory elements are well developed, not only as tubercles, between the lobes on the inner side of all upper true molars. In the latter the following condition is found. On the hindmost upper molar a single tubercle is seen in connection with the anterior lobe of the inner side. On the middle and foremost upper molars, two accessory elements are found close to each other between the inner lobes and belonging one to either of them ; thus anterior as well as posterior accessory elements are present. On the outer side of the middle and hindmost upper molars a similar tubercle is developed from the posterior lobes, and all mandibular molars carry such a tubercle on the outer side of the posterior lobes. In the largest species, Cephalophus sylvicultrix (Afzelius)2, the accessory elements are present on the inner side of the upper molars, and arranged in such a manner that those in the foremost and middle molars belong to the posterior lobes, but in the hindmost molar originate from the anterior lobe. In the mandibular molars of the same species, accessory elements are found between the lobes of the outer side. But in this species the accessory elements have been modified into high columns, especially on the upper molars, in correspondence with the development of the molars to the hypselodont type. I do not think that it can be regarded as hazardous to draw the conclusion from this, that all these accessory elements of the molars are of the same morphological rank although differently developed in various species, depending upon the varying conditions of life and the adaptation to the same. But if this statement is accepted, as I hope it will be, there is no need to postulate any close kinship between such Cavicornia as are provided with accessory columns to the molars. They need only to be derived from more primitive forms which have been able to develop accessory tubercles, out of which the columns have been independently formed with the development of a hypselodont dentition. Consequently the presence of the small accessory columns of Ovibos need not suggest any relationship between this 1 ' Die Rinder der Tertiar-Epoche, 'p. 38. 2 This species does not seem to have to have been recorded from the Cameroons before. Mr. Linell, a Swedish planter residing at Cape Debundscha, has sent borne the flat skin and the skull of a young, but probably full-grown female of this species. |
