In the year 1849 my father, the late Sir John Tomes, (1) described the structure of Marsupial enamel, showing that the enamel was penetrated, more or less richly, by tubes running into it from the dentine, a thing unusual in other Mammalia. But, in the Marsupials, with the solitary exception of the Wombat, it is universal, although in some, as for example in Petaurus , only a few of the tubes enter; and in the Dasyuridæ they are far less abundant, and traverse a smaller thickness of the enamel than in the Macropodidæ. In the latter, the tubes are exceedingly abundant, most of the dentinal tubes being apparently continued into and through the greater part of the thickness of the enamel; they become finer as they approach the surface, and none of them quite reach it; sometimes an enamel tube is connected with two dentinal tubes, and sometimes (rarely) the converse is the case.