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Show 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. Simpliciden ta ti. 1. Muridae. 2. Spalacidae. 3. Dipodidae. 4. Myoxidae. 5. Saccomyidae. 6. Castoridae. 7. Sciuridae. 8. Haploodontidee 9. Chinchillidae. 10. Spalacopodidae. 11. Hystricidae. II. Duplicidentati. 12. Lagomyidee. 13. Leporidae. In his recent work on Scandinavian mammals*, Professor Lilljeborg retains the above arrangement, adding a new family, allied to the Muridae, for the reception of Milne-Edwards's genus Lophiomys. As it became clear that the cranial characters of the groups proposed 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; nevertheless 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 development. 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 Myomorphi. 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 while 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 divisions, it should be premised that an absolutely equal value is not * Sweriges och Norges Ryggradsdjur, I. Daggdjuren. Upsala, 1874. |
