64 MR. E. R. ALSTON ON THE ORDER GLIRES. [Jan. 18, 



first six, the Sciuromorphi the seventh, and the Hystricomorphi 

 the eighth to eleventh families in the following Table : — 



Glires. 



In his recent work on Scandinavian mammals*, Professor Lillje- 

 borg retains the above arrangement, adding a new family, allied to 

 the Muridse, for the reception of Milne-Edwards' s genus Lophiomys. 



As it became clear that the cranial characters of the groups pro- 

 posed by Waterhouse and Brandt are liable to exceptions, and that 

 they are connected by more or less intermediate forms, they have 

 not been regarded with favour by recent systematic writers; never- 

 theless the affinities which they indicate have been very generally 

 accepted in the arrangement of the families. But if a group is a 

 natural one, it should not, I think, be rejected because it is difficult 

 to characterize. The Insectivora may be taken as an example of a 

 very natural order, of which, in Professor Huxley's words, " it is 

 exceedingly difficult to give an absolute definition." Even if it 

 were not possible to separate the first three of Waterhouse' s great 

 families by perfectly constant characters, they ought, as it appears 

 to me, to be recognized as indicating three distinct lines of develop- 

 ment. But by the help of the characters of the leg-bones, pointed 

 out by Professor Lilljeborg, the difficulty is overcome. In the few 

 cases in which the cranial differences fail us in separating the 

 sciurine rodents from the murine, and the latter from the hystricine, 

 the complete ankylosis of the lower part of the tibia and fibula in 

 the second group comes to our aid. As far as I am aware, there is 

 no real exception to this rule ; for the union between these bones 

 sometimes observed in the genus Pteromys, in aged individuals of 

 Castor, and in several of the hystricine series, is totally different 

 from the true fusion which we meet with in all the known Myomor- 

 phi. The first and third groups, which agree with one another in 

 this point, are at once separated from each other by the form of the 

 mandible, as well as by the whole type of cranial structure. 



But wdiile recognizing these groups as true and natural, I cannot 

 consider them to have any thing like the rank of Brandt's Lagomor- 

 phi, and rather treat them as sections of Lilljeborg's suborder Glires 

 Simplicidentati, of somewhat similar value to the sections instituted 

 by Turner and Flower in the Carnivora fissipedia. 



Before proceeding to some general remarks on these various divi- 

 sions, it should be premised that an absolutely equal value is not 

 * Swerigesoeh Norgee Ryggradsdj ur, I. Daggdjuren. Upsala, 1874. 



