IV.—On the Placentation of the Sloths. (Plates III.—V1)) 
By Professor TURNER. 
(Read May 19, 1873.) 
CONTENTS. 
PAGE Pacr 
Introduction, . f 5 5 ; 3 71 General observations on the Placentation 
Uterus and Placenta, : : 3 : 73 of the Edentata, . : j ; : 88 
The Foetus and Epitrichium, . : : 84 
Comparative Anatomists have long been desirous to obtain detailed infor- 
mation on the Placentation of the Sloths. The only observations on this 
- subject which appear to have been made up to this time have been recorded 
by Professor Rupotrut of Berlin,* and Dr C. G. Carus of Dresden.t- Rupotpr 
in the course of some remarks on the structure of the umbilical cord in 
Bradypus tridactylus incidentally mentions that the placenta was cotyledonary 
as in the Ruminants. Carus figures the placenta and an almost mature foetus | 
of a B. tridactylus which came into his possession in 1830. He gives no descrip- 
tion, however, of the specimen, but contents himself with a brief explanation 
of his engraved figures; in the course of which he says, that the specimen 
seemed to him important on account of the length of the umbilical cord, 
and the form of the cotyledons, which did not project, as is usual, outwards, 
but towards the inner face of the ovum, a peculiarity which had not yet been 
observed and described. 
The complete absence of any description by these anatomists of the struc- 
ture of the sloth’s placenta, the brevity of their observations on its form, and 
the want of any explanation of the sense in which they use the term cotyledons, 
have afforded room for a considerable amount of speculation as to the character 
of the placentation in these animals, and have led to the expression of very 
diverse opinions, as may be gathered from the comments which have been 
made in the writings of eminent anatomists both in this country and abroad. 
Von Baer states,{ “The ovum of the Tardigrada is a remarkable intermediate 
form between the very heterogenic placentze of the Apes and the Ruminants. It 
* Ueber den Embryo der Affen und einiger anderen Saugethiere, in Abhandl. der Akad. der 
Wissensch. zu Berlin, 1828. 
+ Erlauterungs Tafeln zur Vergleich. Anatomie Heft III. Plate IX. Leipzig, 1831. 
t{ Ueber Entwicklungs-Geschichte der Thiere, p. 263. 1837. 
VOT exeov LI: WPART I. Tt 
