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 Rodenfia 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 Wjombat 

 approached very near to the Rodents) it would have been fui'ther 

 necessary to point out the species of Rodents which linked the 

 order, of which they formed part, with the AYombat. Cu^•ier 

 observed that this animal was gradually hnked with other Marsu- 

 jiiata (veiy dissimilar to the Rodents) by intermediate species, 

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

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

 on the Rodent side. A thorough examination of the Wombat 

 and nimierous other Marsupialia has now sho'«Ti 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 tj'pe than has hitherto 

 been observed in any of the Placental series : this is ednced 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 yoxmg or wgin 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 gi-eat an extent of the vagina and as a permanent struc- 

 tm-e." 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 ajjproach to the Marsupiata, 

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

 bom-ing groups I cannot perceive, on the one hand, any traces in 

 the Wombat of the pecuhar 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. 



