M 



R. W. F. R. WELDON ON THE PLACENTATION [Jan. 15, 



the uterus, each being borne on a constricted neck, mucb as in the 

 Sheep (fig. 4). The average diameter ofeach cotyledon was 25 mm., 

 though some were larger and some smaller. 



There were also (fig. 2) occasional patches, each of some six or eight 

 large villi, in various parts of the chorion. 



The allantoic diverticulum was well developed (fig. 3, al). 



The point of interest, however, about this placenta, is the exis- 

 tence over the whole surface of the chorion of vascular ridges, fitting 

 into corresponding depressions of the uterine epithelium, and exactly 



Fig. 2. 



Diffuse ridges of the placenta of Tetraceros quadricornis. 



resembling those ridges which form in the Pig the whole placental 

 apparatus. 



The velvety appearance, due to these folds, is more or less suc- 

 cessfully represented in fig. 3 ; while a view of the chorion under a 

 low magnifying-power is shown in fig. 4, where it is seen that the 

 vascular ridges form an irregular network, into the meshes of which, 

 between the ridges, open the numerous uterine glands (fig. 4, u.gl.). 



It will be seen, from what has been said, that this placenta is 

 exactly intermediate in structure between the completely diffuse 

 placenta of Moschus on the one hand, and the complex cotyledonary 

 apparatus, of the Sheep for example, on the other. Tetraceros 

 therefore stands, as far as its placenta is concerned, in the same place 

 in the Antelope series as that occupied by Cervus mexicanus in the 

 Cervine series. 



