Teeth in the Centetide. 533 
For my part I have not ventured to trace the form of molar 
seen in Tertiary mammals to that of the older Mesozoic fossils, 
because, on the one hand, the hiatus between the faune 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 the majority of 
fossil remains from the Purbeck, Stonesfield, &c. is demon- 
strated beyond the possibility of doubt. 
We are upon firmer ground with regard to a portion of the 
Laramie mammals, which unhappily 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 ‘T'rituberculata *; in the 
following comparison with the Insectivora we have to deal 
with the latter alone. The best-preserved upper-jaw teeth 
among these f 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 Didelphyide, Dasyuride, 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 Didelphyide, and to which, flanking the talon on the 
outer side, are, moreover, superadded two smaller intermediate 
tubercles—the protoconule 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 Galeopithecus, Urotrichus, 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, pl. vii. 
+ Loe. cit. pl. viil. 
