92 PROFESSOR TURNER ON THE PLACENTATION OF THE SLOTHS. 
tain the mode in which they opened on the surface of the mucosa, which 
was thickly studded with minute pits or fosse; it is probable, however, that 
they opened obliquely into the bottom of these pits. The free surfaces, both 
of the chorion and uterine mucosa, presented, without doubt, the appearance 
which one recognises as characteristic of a diffused non-deciduate placenta. 
The placenta, therefore, in Manis, differs in several most important parti- 
culars, both in arrangement and structure, from what I have described in 
Cholepus. Not only is it diffused and non-deciduate, but both the allantois 
and umbilical vesicle remain as distinct sacs, and the utricular glands persist 
throughout the gravid uterine mucosa. 
The demonstration, therefore, of the diffused, non-deciduate character of the 
placenta in Manis by Dr Suarpey, and of the multilobate, discoid, deciduate 
placenta in Cholawpus by myself, will render it necessary for the systematic 
zoologist to reconsider either the value of the placenta as the basis of a system 
of classification, or the propriety of retaining the Sloths and the Scaly Ant- 
eaters in the same order. If the characters of the placenta are tu be regarded 
as of more importance in classification than those furnished by any other 
organ or combination of organs, then it is clear that the non-deciduate Manis 
can no longer be placed in the same order as the deciduate Tardigrade. But 
if the characters of the other organic systems in the animals belonging to the 
order Edentata, as at present accepted, exhibit a series of affinities, which to 
the mind of the zoologist may seem to out-weigh the differences in placental 
structure, not only between Manis on the one hand, and Cholepus, Dasypus, 
and Orycteropus on the other, but, if my inference as to the deciduate nature of 
the placenta in Myrmecophaga be correct, between Manis and Myrmecophaga 
also—affinities which would render it advisable that they should be retained in 
the same order,—then the placental system of classification is obviously not 
universally applicable, and will have to be abandoned. It would be out of place 
in this communication to enter into the consideration of the anatomy of the other 
organic systems in Cholapus, and to discuss how far its various organs resemble, 
or differ from, those of the genera with which it is usually associated ; but I 
hope, from the materials in my possession, to supplement this memoir, and 
draw up, in the course of the next few months, a detailed account of the struc- 
ture of this animal, and to compare it, as far as the materials at my disposal will 
allow, with the other animals usually grouped with it in the order Edentata. 
Before bringing this memoir to a conclusion, it may not be without interest 
briefly to compare the placentation of the Sloths with that of the other orders 
of Deciduate mammals. 
It may help to make this comparison more complete if I introduce here 
some observations which I have recently made on the structure of the un- 
impregnated uterus of the Sloth. Through the kind permission of Dr ScLaTER 
