Teeth in the Centetulaj. 533 



For my )iart 1 liave not ventured to trace the form of molar 

 secTi in Tertiary mammals to that of the older Mesozoic fossils, 

 because, on the one hand, the hiatus between the faunae of 

 the Lower Eocene and those of the Jura has hitherto been too 

 great, and because, on the other, all sorts of data are still 

 requisite before the mammalian nature of tho majority of 

 fossil remains from the Purbeck, Stonesfield, &c. is demon- 

 strated beyond the possibility of doubt. 



^^'e are u[)on firmer ground with regard to a portion of the 

 Laramie mammals, which unha])pily are for the moment still 

 very few in number and generally isolated. Here, in the 

 Upper Cretaceous, we meet, almost without exception, with 

 polybunous teeth, and this, indeed, equally among the Multi- 

 tuberculata as among the so-called Trituberculata * ; in the 

 following comparison with the Insectivora we have to deal 

 with the latter alone. The best-preserved upper-jaw teeth 

 among these t are remarkable, in the first place owing to the 

 extraordinary development of the external series of cusps, to 

 only two of which Osborn gives names — parastyle and meta- 

 style — while, as in the case of Didelphyida?, Dasyuridie, and 

 Insectivora, from four to five cusps are present ; in the second 

 place owing to the considerable vertical and horizontal extent 

 of the internal talon (" protocone "), which is even bulkier 

 than in Didelphyidfe, and to which, flanking the talon on the 

 outer side, are, moreover, superadded two smaller intermediate 

 tubercles — the jyrotoconule and metaconule. In correspondence 

 with this, the talon (^' talonid ") on the lower molars also is 

 remarkably strongly developed. 



Among Insectivora we meet with a similar profusion of 

 tooth-cusps in GaleoijithecuSj UrotrichuSj Myogale, &c. ; these 

 genera, however, in addition to this show specialization in the 

 shape of a commencing solenodonty. The external cusps 

 have diminished in bulk; similarly the talon also of the upper 

 molars is of more moderate dimensions than in the teeth from 

 the Cretaceous, and the " intermediate tubercles " are corre- 

 spondingly enlarged. In Myogale the hindmost of the latter 

 — the *' metaconule " — has shifted its position more towards 

 the inside, and, at least in the case of M. 1, it is almost equal 

 to the talon in bulk : the question suggests itself whether we 

 may not find herein an indication of the mode of origin of 

 many " quadritubercular " mammalian molars. 



Potamogale. — In this genus, as has been mentioned above, 



* H. F. Osborn, " Fossil Mammals of the Upper Cretaceous Beds," 

 Bull. Amer. Mus. of Nat. Hist. vol. v. 1893, pi. viii. 

 t Loc. cit. pi. viii. 



