Mr. G. R. Waterhouse on the Classification of Mammalia. 405 



these last to the Wombat ; and, finally, if it were not that the 

 organs of generation in that animal were perfectly similar to those 

 of all belonging to the family Marsupialia." The Wombat then 

 is an animal which appeared to link two orders or large sections, 

 the Rodentia and the Marsupiata ; but this case would have 

 been insufficient to support the belief that these two groups very 

 gradually blended into each other ; for (admitting the Wombat 

 approached very near to the Eodents) it would have been further 

 necessary to point out the species of Rodents which linked the 

 order, of which they formed part, with the Wombat. Cuvier 

 observed that this animal was gradually linked with other Marsu- 

 piata (very dissimilar to the Rodents) by intermediate species, 

 and mentions that fact as one which induced him to place it in 

 the Marsupiate division, but he does not point out similar links 

 on the Rodent side. A thorough examination of the Wombat 

 and numerous other Marsupialia has now shown that these ani- 

 mals are much more closely connected than was supposed ; most 

 important peculiarities in these animals have been discovered, 

 and the degree of relationship which the animal under consider- 

 ation bears to the Rodents must in proportion be modified. On 

 the other hand. Prof. Owen, in his dissection of a certain Rodent 

 (the Biscacha*, Lagostomus trichodactylus), has discovered pecu- 

 liarities in the female generative organs of that animal in which 

 it approaches nearer to the Marsupial type than has hitherto 

 been observed in any of the Placental series : this is evinced in 

 the presence of a longitudinal septum dividing the vagina into 

 two canals for upwards of an inch beyond the ora tincce ; " ru- 

 diments of a vaginal septum,^^ the Professor remarks, " occur in 

 the young or virgin state of several genera ; but it is only in the 

 Lagostomus that a continuation of the median separation of the 

 genital tubes has been continued beyond the uterine portion 

 along so great an extent of the vagina and as a permanent struc- 

 ture.^' Let it be added to this, that in the order Rodentia, ge- 

 nerally, other characters have been pointed out which indicate 

 that this group evinces the nearest approach to the Marsupiata, 

 yet as regards the two nearest species respectively of these neigh- 

 bouring groups I cannot perceive, on the one hand, any traces in 

 the Wombat of the peculiar characters which distinguish the 

 Lagostomus, or the little family to which it belongs, from other 

 Rodents, and vice versa. There is, in fact, a considerable hiatus 

 between the two groups. The Lagostomus is essentially a Rodent, 

 but being one of the members of an order which in the Placental 

 series is perhaps, on the whole, the furthest removed from the 

 head of that series, and also it being certainly one among the 



* Proceedings of the Zoological Society for December 1839, p. 177 ; Ann. 

 Nat. Hist. vol. vi. p. 68. 



