466 DR. C. I. FOESTTH MAJOR ON 



superior incisor " hns the external groove less deep, and placed nearer to the inner edge 

 of the tooth," than in the Common Hare * ; and W. T. Blanford states of Lopiis dmjamis, 

 Blf., that "the upper incisors appear very indistinctly grooved " f. The species 

 mentioned are precisely among those in which the groove of the upper incisors 

 is very deep ; but they present the appearance of being shallow, owing to the cement 

 which incompletely fills them. In fact, the cement appears in all species in which 

 the groove penetrates further backward than in the commonly accessible species 

 (i. eui'OjJcBUS, Oryctolagus cunioulus), and it is in that case very often associated with 

 other complications which we have now to consider. 



Hodgson gives as one of the distinctive characters of Oaprolayiis hispidus the 

 following : — " the groove in fi'ont of the upper incisors is continued to their cutting-edge 

 so as to notch it " |. Strictly speaking, the cutting-edge of the upper leporine incisors is 

 always notched — even in Lepus europcBus ; only, in C. hisp/'dus (text-fig. VIII), the 

 groove, filled with cement, is much broader and penetrates further backward, so that 

 the natural section presented when the incisor is viewed from its lower side (same fig.) 

 shows the groove under the form of a A^ery elongated triangle, with the apex at its 

 posterior end. A more complicated form has been noticed by Hilgendorf, as stated in 

 the following brief sentence: — "Die oberen Schneidezahne von Lepus caUotis aus 

 Mexico uud Lepus nigricollis aus Indien sind gabelig schmelzfaltig (dentes complicati) ; 

 die entsj)rechenden ZJihne der afrikanischen Hasen bilden durch eine einfachere 

 Einbuchtung des Schmelzes einen Uebergang von jenen zu den anderen Hasenarten" §. 

 In a later note by the same writer fiirther particulars are given ||. In the text- 

 figures I-XXIV are shown, enlarged (about 4x1), the principal modifications of 

 the enamel-folding of upper leporine incisors viewed from below and with the anterior 

 border directed downward. Some slight difi'crences between the few descriptions 

 given by Hilgendorf and my figures of the supposed same species are apparently 

 due to different causes : in the first place, because Hilgendorf describes tooth- 

 sections. Moreover, specimens of the same species may vary slightly {of. figs. XVI & 

 XVII), owing partly to individual variation. But the shape of the enamel-fold varies 

 equally at different stages in the age of the animal ; species whose incisors show the 

 most complicated pattern in the adult have as yet no trace of this in very young 

 animals ; and, vice versa, in very old specimens complication tends to disapj)ear again. 

 As shown by several of the text-figures, slight variations between the right and left 

 incisor of the same individual also occur. These circumstances will, of course, iiave 

 to be taken into account for systematic purposes. 



The most complicated folding in Hilgendorf's inateinal was i)resented by a L. callotis, 

 Wagn. (=i. mexicanus, Lichtenst.), from Mexico ^, in the shape of a T, whose transverse 



* Op. elf. p. 77. — R. Swinhoe (Proc. Zool. Soc. Loud. lcS70, p. 234) makes a similar remark with regard to 

 L. haiiuinus. 

 t W. T. Blanford, -'On New Mammals from Sind," P. Z. S. London (lS7-f), p. (563. 

 J Jouru. As. Soc. Bengal, xvi. 1, p. 576 (1846). 

 § Sitzungsber. Berl. Ak. Wiss., Sitzg. 14 Dec. 1865 (1866). 

 II Sitzungsber. Ges. naturf. Freunde Berlin, Sitzg. 15 Jan. 1884, pp. 18-21. % Op. cit. pp. 18, 19. 



