Thomas, Catalogue of Monotremata and Marsupialia in the British Museum (1888); "On Caenolestes, a Survivor of the Epanorthidae," Proc. Zool.
There are two orders, the Marsupialia and the Monotremata, which do not possess this organ; both these are found in Australia, to which region indeed they are not absolutely confined.
We pass on to the other curious order of non-placental mammals, that of the Monotremata, so called from the structure of their organs of evacuation with a single orifice, as in birds.
Latreille 6 published a new classification of the Vertebrata, which are primarily divided into Haematherma, containing the three classes of Maminifera, Monotremata and A y es; and Haemacryma, also containing three classes - Reptilia, Amphibia and Pisces.