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Show 1897.] MALAGASY GENUS BRACHYUROMYS. 707 same longitudinal row. Winge has summed up in a few words his view of the fate of these outer cusps l. But in the figures of upper Kodent molars he ignores what I consider to be their homologues. Eor a clearer understanding of what is to follow, I append two sketches of the same upper molar from Winge's plates, the first with the numbering given by this author, the second with the numbering according to the manner in which I grasp the homologies. The tooth figured is one of the Hesperomyince with more complicated molars, being a copy of fig. 12a, pl. iii. of Winge's paper2, representing the second right upper molar of " Nectomys squamipes" (text-figs. 1 and 2). Winge assigns the homologies Eig. 1. Fig. 2. "7 \ 7'ty'- Second right upper molar of Nectomys squamipes, after Winge. 5 4 thus : s-g, taking into consideration only what in these teeth appear to be the principal cusps; whereas I would write them as 3 5 2 4 1 . . follows : - s - ^ - , taking into consideration as well those which in these teeth appear to be merely secondary cusps3. N o w as to Brachyuromys. Here we have as principal feature of the molars three transverse and somewhat oblique rows. Iu Brachyuromys ramlrohltra the separation of the three rows, their obliquity and their lophodontism are more pronounced than in B. betsileoensis, whose unworn teeth show a half-tuberculate conformation and are therefore more fit for the understanding of the homologies. M. 2 sup. (Plate X X X I X . figs. 1 a, 2 a, 3 a, 7 a, 8 «).-The anterior transverse row apparently is composed of the outer cusp 1 and the inner .cusp 6. The second one is a compound, on the outer side, of ' 4' anteriorly and ' 2 ' posteriorly, which in very early stages become fused with each other and with the inner cusp 7. The most prominent outer and inner cusps, 1 " Kronen bliver ved sin Vrext saa bred, at Underkjajbe tasnderne ere for smalle til endnu at rore ved dens ydre Rand, naar Munden lukkes ; derfor vantrives de tre oprindelige yderste Spidser og indskrtenkes til fremspringeude Hjcerner eller Lister, smelte sammen med de naermeste indre Spidser ellerfors-vinde belt" ( O m Pattedyrenes Tandskifte, etc., /. c. pp. 17,18; see also footnote 4 on p. 41). 2 ' Gnavere fra Lagoa Santa, etc.' 3 O n comparison of the lower molars figured in Plates X X X I X . and X L . of tbe present paper with those on pl. iii. of Winge's " O m Pattedyrenes Tandskifte, etc.," it will be seen that m y mode of numbering tbe cusps tu indicate their homologies disagrees with the one adopted by Winge; but I cannot in this paper enter into a discussion of m y mode of viewing the homologies of lower molars. |
