Contributions to our Knowledge of the Structure of the Placenta of Mustelidæ, Ursidse, and Sciuridæ

S ummary . The chief features of the placenta of Xerus capensis are:— It is discoidal and mesometrially situated. It is hæmochorial in type. The lamellæ appear to form a simple anastomosing network and the lacunæ are wide. The “lobed” arrangement characteristic of the Rabbit placenta is absent. There is no interplacental cavity. The extraplacental wall of the uterus is very thick. Giant cells form a characteristic feature of the placenta. The yolk‐sac splanchnopleure is simple, being devoid of folds and villi. The trilaminar omphalopleure persists and forms the foetal constituent of the yolk‐sac placenta.