On the Dentition of Didelphys. 285 
formation from reptile-like progenitors, a number of simple, 
conical reptile-teeth came together to form each mammalian 
molar? Paleontology is in favour of my view; the oldest 
known mammals, e. g. Triconodon from the Upper Jura, 
exhibit molars of the typical structure requisite for our idea, 
each consisting of three similar conical tooth-segments, lying 
one behind the other and fused together. The admirable 
papers of Cope, Osborn, Schlosser, and others have shown 
that from the triconodont, that is the tricuspid type, the 
molars of all mammals may be derived. 
A multitude of questions as to the specialization of the 
teeth within the various orders, the teeth with continuous 
erowth, the formation of roots, &c., still remain to be 
answered ; I shall make the attempt to do this in a detailed 
account of my investigations. 
Jena, June 5, 1891. 
XLIV.— The Dentition of Didelphys: a Contribution to the 
Embryology of the Dentition of Marsupials*, By W. 
KUKENTHAL f. 
In the case of Didelphys the dental formula 5 + 3G is very 
generally accepted. The tooth-change is limited to one 
tooth, the last premolar, as was first discovered by Gervais 
and Flower to be the case in Marsupials. By this discovery 
the older view that in Marsupials the whole of the teeth are 
replaced with the exception of the four molars was finally 
overthrown. The question, however, now arose as to how 
the dentition of Marsupials was to be regarded, ¢. e. whether 
it corresponds to the milk-dentition or to the permanent series 
of other, Mammals. While Owen was rather inclined to 
adopt the former view, the latter was maintained by Flower, 
_* Tyanslated from a separate impression from the ‘ Anatomischer 
Anzeiger,’ vi. Jahrgang (1891), nos. 23 and 24, pp. 658-666. 
+ In a paper which was recently published in this periodical, entitled 
“Binige Bemerkungen iiber die Siiugetierbezahnung” (Anat. Anz. 
1891, p. 369 [wide supra, “ Observations on the Dentition of Mammals,” 
pp. 279-285 ]), I have already alluded to the chief result of my investiga- 
tions, which formed the subject of an address delivered on the 30th of 
May of the present year in the Aula of our University. But, in conse- 
quence of the delay which has arisen in the setting-up of my detailed 
statements owing to the compositors’ strike, I am now induced to give 
herewith a somewhat closer proof of my assertions, at least as regards the 
Marsupials. 
