X. 



ON THE PLACENTAL STRUCTURES OF THE 

 TENREC (CENTETES ECAUDATUS) AND 

 THOSE OF CERTAIN OTHER MAMMALIA; 

 WITH REMARKS ON THE VALUE OF THE 

 PLACENTAL SYSTEM OF CLASSIFICATION. 



Having, through the kindness of Alfred Newton, Esq., F.Z.S., 

 come into possession of a female tenree {Centetes ecaudatui), I pro- 

 pose to lay before the Society a description of its generative organs, 

 and of certain foetal structures which were found in connexion with 

 them. To this I shall append descriptions of the homologous 

 structures in several other mammalia, comparing them inter se, as 

 well as with what I believe will prove to be the unique modifications 

 of the placenta in the tenree ; and throughout the paper I shall 

 keep in view the bearing which the facts detailed may have upon 

 the morphological value of differences in the structure of the 

 placenta. 



i. Female Generative Organs. 



The urethro-sexual and anal outlets open within a single ori- 

 fice, on either side of which there is a saucer-shaped depression, 

 such as exists within the rabbit, underlain by a cluster of all but 

 sessile glands, with which racemose anal glands, possessing ex- 

 cretory ducts converging to one common pedicle, co-exist. The 

 urethro-sexual canal is seven-eighths of an inch in length ; its 

 walls are smooth internally, and it receives on either side the duct 

 of a Duvernoy gland. The vagina is divisible into two portions, 

 the lower part of the tube being smooth and patent internally, 

 whilst the upper has its canal more or less perfectly obliterated by 

 the interlocking of inwardly growing transverse processes of its 



