88 PROFESSOR TURNER ON THE PLACENTATION OF THE SLOTHS. 
the embryos of these animals, therefore, it would appear that the urachus 
persists longer than it does in Cholapus. 
General Observations on the Placentation of the Edentata.* 
From the description which I have now given of the form and structure of 
the placenta in this specimen of Cholwpus, and from the accurate interpretation 
which I am able to offer of Carus’s figure of the placenta in Bradypus, it is 
evident that in the Sloths the placenta is not cotyledonary, 7.¢.,—if we use the 
term cotyledon, in the sense in which it is usually employed by zoologists, to 
express a particular form of non-deciduate placenta,—subdivided into distinct 
and scattered masses as in the Ruminants. It can only be called cotyledonary, 
if the term be employed, as is sometimes done in speaking of the deciduate 
human placenta, as equivalent to lobes. To avoid confusion in the use of terms, 
it may be well to speak of the sloth’s placenta as a dome-like, multilobate, aggre- 
gate placenta, the lobes of which are discoidal. It is a deciduate placenta in 
the fullest sense of the word ; for not only is a decidua reflexa shed along with 
the fcetal membranes, but if the plane at which I separated the placenta 
from the uterus be, as I think there can be no doubt it is, the natural plane 
of separation of these parts during parturition, then the foetal membranes carry 
away with them the deciduous serotina, the curling arteries, the utero-placental 
veins, and the intra-placental maternal vessels. I have been able, therefore, to 
put on the basis of an actual demonstration the deciduate structure of the 
placenta in the Sloth, which RoLieston, Owen, and Mitne Epwarps from the 
study of Carus’s drawing, had regarded as not improbable. 
The character of the placentation in the Sloths having now been determined, 
it will be interesting in the next place to compare it with what has been 
recorded respecting the placentation of the other mammals included in the 
order Edentata. Unfortunately, however, we are not provided with such 
detailed information relative to the placental characters of these animals as to 
enable one to make so complete and exact a comparison as could be desired. 
Any remarks, therefore, which may be based on this comparison must be 
regarded as provisional merely, and to be subject to revision when more precise 
knowledge is obtained. 
Of the placenta of the Armadillos nothing further has apparently been 
recorded than is contained in the brief statement made by Prof. Owen + that 
it is a single, thin, oblong disc, with which the maternal deciduous substance 
is interblended. 
Our information as to the placenta of Orycteropus is also equally brief, and 
is limited to the observation recorded by Prof. Huxuey in his “ Introduction 
* November, 1873.—This section has been re-written and added to since the paper was read. 
t+ Anatomy of Vertebrates, iii., p. 731. 1868. 
