494 Dr. C. I. Forsyth Major — On Fossil Bornnce. 



showing that the fossil species differs from the recent in the number 

 of roots of the upper teeth. A small fragment of the upper jaw 

 exhibits the alveolus of the premolar and that of the first true 

 molar. The former shows that the upper premolar had three 

 distinctly separate roots, like the first true molar, though minuter 

 and more crowded together than in the latter. In both, two minute 

 roots are situated externally, a larger one internally. This con- 

 formation of the roots of Mnscardinvs Snnsnniensis is confirmed by 

 an examination of the fossil jaw from La Grive, from which it further 

 appears that the three roots of m. 2 and m. 3 are arranged in the 

 same manner as in the anterior teeth. 



In Muscardinns avellanarius the upper premolar is one-rooted. 

 The roots of the first true molar are described by Nehring as 

 follows: " Der erste (langgestreckte) Molar besitzt fiinf Wurzeln, 

 deren Alveolen so gestellt sind, dass sie ein Trapez bilden ; drei 

 derselben liegen an der Gaumenseite (die mittlere ist sehr zart), die 

 beiden andern finden sich an der Aussenseite des Kiefers." The 

 second and third upper molar each exhibit four roots.^ 



The lower jaws from Ija Grive at my disposal are: (1) A right 

 mandibular ramus (Geol. Dep., No. M 5.300), in which only m. 2 is 

 preserved. Length of the alveoli of the four cheek-teeth 3|^ mm., 

 as in the upper jaw from the same deposit. (2) A fragmentary 

 right I'amus, exhibiting the first and second true molars. Amongst 

 the small fragments from Sansan in the Geological Department 

 (No. 33,274) is (1) a mandibular fragment, right side, showing the 

 empty alveolus of the premolar, and the first true molar ; (2) a 

 fragment of a right ramus, in which are preserved the first and 

 second true molars. The general character of all these teeth is that 

 of those of the upper jaw. Their crown is perfectly flat ; the 

 transverse ridges show no tendency to form tubercles at either the 

 outer or the inner margin, although some of the crests join together 

 on the outer and on the inner side. This occurs likewise in the 

 recent Muscnrdinus avellannrivs, but to a lesser extent than in the 

 fossil. M.l is of slightly less size — shorter and narrower — than 

 m. 2, and considerably shorter than m.l of Muscardinns avellanarius, 

 also diifers from it in the same manner as does the corresponding 

 upper tooth of the fossil from that of the recent form. This tooth 

 in the fossil is almost square ; the posterior margin, however, is 

 broader than the anterior. The number of transverse ridges is six 

 in both the fossil teeth preserved (m.l and ra.2), besides some 

 incomplete intermediate ridges situated near the inner side. In one 

 m. 1 of La Grive, a much worn tooth, I observe only five complete 

 ridges. 



From the alveoli preserved, the number of roots can be made out 

 as follows : one in the premolar, two in the true molars. In the 

 recent species the lower premolar has likewise one root, m. 1 three 

 roots, m. 2 four, m. 3 three.^ 



1 A. Nehring, " Zura Zahnsystem der Myoxinen" : Zeitschr. Gesammt. Naturw., 

 1879, p. 739. . 

 - Kehriug, loc. cit. 



