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VII. On the Placental Structures of the Tenrec (Centetes ecaudatus), and those of certain 

 other Mammalia ; ivith Remarks on the Value of the Placental System of Classification. 

 By Professor Rolleston, F.R.S., F.Z.S., &c. 



Read June 23, 1863. 

 [Plate L.] 



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

 of a female Tenrec {Centetes ecaudatus), I propose to lay before the Society a description 

 of its generative organs, and of certain festal 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 Tenrec ; 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. 



1. Female Generative Organs. 



The urethro-sexual and anal outlets open within a single orifice, on either side of 

 which there is a saucer-shaped depression, such as exists in the Rabbit, underlain by a 

 cluster of all but sessile glands, with which racemose anal glands, possessing excretory 

 ducts converging to one common pedicle, coexist. 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's 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 trans- 

 verse processes of its walls. The lower part of the vagina is one inch in length ; the 

 upper is one inch and an eighth. The interlocking processes developed from the 

 walls of the upper part leave a pervious passage from below upwards for about half 

 the length of this part of the tube ; the uppermost half, however, is entirely blocked up 

 by the formation of complete transverse septa. Upon one of these, at a distance of 

 three eighths of an inch from the commencement of the uterine cornua, an os tinc(e-\ike 

 projection, a quarter of an inch long, but ending blindly, is developed. Its presence 

 may make it doubtful whether the portion of the sexual canal, with the interlocking 

 processes developed upon it, does not correspond to parts both of vagina and of corpus 

 uteri. Somewhat similar processes are figured by C. G. Carus' in the Kinkajou 

 {Cercoleptes caudivolvulus) in the vagina alone, the corpus uteri having been left uu- 

 ' C. G. Carus, 'Tabulae Anatomiam Comparativam lUustrantes,' pars v. tab. viii. fig. 6, 1840. 



2 p2 



