FOSSIL AND EECENT LAGOMOKPHA. " 455 



effect that the roots of the deciduous teeth of Prolagus have a coating of enamel : " sie 

 hesteheu geuau aus derselben Sehmelzmasse, wie die Zuhnbiichse selbst, die das Zahnbein 

 umg-iebt " *; and secoudly the fact that in some instances he seems to have mistaken 

 foi' roots what in reality are tlie tul)e-like lower terminations of the enamel folds. 



In the first tooth of the ujjper series (p. 3, PL 36. fig. 21) the two enamel folds are 

 also present ; they penetrate into the surface of the crown from its anterior side 

 and run in a longitudinal direction. The anterior liorder ('• wall ") of the triturating 

 surface, already sliglitly shortened in p. 2, is still more shortened in p. 3, being reduced 

 to a short longitudinal stump on the antero-internal corner. 



From what has previously been stated, we are prepared to find, in different stages of 

 attrition of these upper teeth, some difference in the pattern ; this is, in fact, what takes 

 place. The enamel islet of m. 2 has disappeared in old specimens ; and such is the case in 

 the specimen figured by Fraasf. The enamel islet of m. 1 varies in size according to 

 age, being larger in younger specimens. The same holds good with regard to the two 

 enamel islets of p. 1. We anticij)ated tliat in young stages of this tooth the enamel 

 islets wouhl have the shajie of enamel folds ojieuing freely on tlie margin of the tooth, 

 as is the case in p. 2. This is, in fact, what happens in young specimens of the following 

 species [P. sardus). Of P. a'ltingeims I have no very young examples. 



P. 2 varies little with age; the notch on the inner side is more distinct in comparatively 

 young individuals, and there is shown in this stage (fig. 10) a third very small enamel 

 fold in the postero-external corner of the tooth, which soon disappears by attrition. 



Deciduous upper teeth ofV. oeningensis. — Fraas has figured the three deciduous upper 

 cheek-teeth iji. situ J ; he scarcely describes their pattern, contenting himself with the 

 statement that the anterior one is well provided with folds (" faltenreich "), and that it 

 presents much resemblance to the second of the permanent dentition §. 



I have only detached upper deciduous teeth, five in number. Two of these are in the 

 British Museum, under M5237, from my collections. The anterior milk-tootli (d. 3) is 

 not represented among these five detached teeth ; according to tlie figure of Fraas, and 

 to what I know of the same tooth of P. sard/is, it has triangular contours ; while the 

 detached teeth at my disposal arc squarish ol:)long, almost tetragonous, their transverse 

 diameter slightly exceeding the longitudinal. They show (PI. 36. fig. 29) an internal 

 notch and two enamel folds, the latter opening freely on the outer side. The internal of 

 the tw^o folds (b) has the form of a crescent and is the larger of the two. The roots 

 are three in number ; the outer two very minute, the inner single one considerably 

 larger ; the former run jjarallel with each other, hut not wdth the odd inner root, whicli 

 strongly diverges from them inward, while tiiey diverge outward (PI. 39. figs. 21, 22). 



Prolagus sakdus. 



Ldyoniys sardus fossilis, Riul. Wagner, Okcii's Lsis, \). 113G (1829). 

 Lagoinys foss'dis. Id. op. cit. jj. 1139. 



* In this there is some trutli ; see above, pp. 446, 447. 



t Op. cit. pi. ii. iig. 6. + Op. cit. pi. ii. fig. 14. § P. 177. 



