1888-89.] Prof. Sir Wm. Turner on the Halicore Dugong. 265 
position to the zone on the chorion. This zone contained multi- 
tudes of short cylindriform crypts, in which the villi of the chorion 
were lodged. Longer and more deeply placed crypts were also 
present for the lodgment of the longer villi. 
The non-placental area of the mucous membrane was smooth, and 
corresponded to the non-villous part of the chorion. 
Uterine glands were seen both in the placental and non-placental 
areas of the mucous membrane. In the placental area they opened 
amidst the crypts by special orifices; in the non-placental area they 
opened obliquely on the smooth surface of the mucous membrane. 
Owing to the shortness both of the chorionic villi and the uterine 
crypts and their simple form, it is believed that the placenta, when 
shed in normal parturition, would be generally non-deciduate, in the 
sense of the vascular walls of the crypts not being shed along with 
the villi; it is not unlikely, as the author showed some years ago to 
be the case in the sheep and cow,* that the epithelial lining of the 
crypts may separate more or less, and pass off entangled between the 
villi. It is also possible that the longer villi may carry away with 
them parts of the vascular wails of their crypts. 
Should the placenta be non-deciduate in the sense that the 
vascular part of the maternal mucous membrane is not shed, then 
the placenta of the Dugong gives a new type of placenta — one 
which is both zonary and generally non-deciduate. 
The diffused character of the placenta in the specimen described 
by Paul Harting was due to its comparatively early stage of develop- 
ment, for the villi had not as yet limited themselves to a denfinite 
zone. 
The paper concluded by a comparison of the placentation of the 
Dugong with that more especially of the Cetacea, Carnivora, and 
Proboscidea, and by remarks on the bearings of the form and 
structure of the placenta on the classification of the Sirenia. 
* Proc. Roy. Soc. Edin., May 1875. 
