G2 MR. E. R. ALSTON ON THE ORDER GLIRES. [Jail. 18, 



These diflficulties were insuperable as long as zoologists placed 

 their trust in outward appearances ; and when sounder principles 

 gained ground it was some time before the necessary anatomical data 

 could he collected. Without detailing all the classifications which 

 have been proposed within the last fifty years, I must briefly men- 

 tion the memoirs of the four zoologists on whose labours, as already 

 stated, the following proposed arrangement is chiefly based. 



In 1839, Mr. G. R. Waterhouse, then Curator of this Society, 

 published the first of a series of essays in which he may confidently 

 be said to have laid down the groundwork of a natural arrangement 

 of this order*. Unfortunately, as the mammalogist must think, 

 this accurate and thoughtful zoologist has long since turned bis 

 attention to other departments, and only a small portion of his great 

 work on the Rodentia ever appearedf. In his first papers Mr. 

 Waterhouse, taking the characters of the skull and mandible as his 

 chief guides, arranged the Rodents into three great families, the 

 Murina, Hystricina, and Leporina, with twelve subfamilies. Con- 

 tinuing his labours for ten years, his views were naturally changed 

 on many points. Latterly he separated the Sciuridcs as a group 

 equal in value to the other two, the following being the arrangement 

 of families and subfamilies adopted in his later writings : — 



Rodentia. 



I. Sciiiridce. III. Hystricidce. 



II. Muridee. 1. Hystricina. 



1. Saccomyina. 2. Dasyproctina. 



2. Dipodina. 3. Echimyina. 



3. Ctenodactylina. 4. Octodontina. 



4. Murina. 5. Chinchillina. 

 .5. Spalacina. fi. Caviina. 



6. Arvicolina. IV. Leporidce. 



7. Bathyergina. 



In 1848 Professor Gervais published an arrangement of this order, 

 in which he instituted two principal sections or subordersj. The 

 first of these included the ordinary Rodents with only one pair of 

 incisors above and below ; the second consisted of those with two 

 pairs in the upper jaw, and was consequently equivalent to Illiger'a 

 group Dujilicidenta^. The following was Professor Gervais' s ar- 

 rangement of the famihes : — 



* "Observations on the Eodentia," Mag. Nat. Hist. iii. pp. 90-96, 184-188, 

 274-279, 593-600 ; Ann. Nat. Hist. viii. pp. 81-84, x. pp. 197-203 (1839-42). 

 " On the Geographical Distribution of the Eodentia," P. Z. S. 1839, pp. 172-174. 

 " Order Eodentia," Keith Johnston's Physical Atlas, Phytology and Zoology, 

 map. 5, letterpress (1849). 



t Natural History of the Mammalia, vol. ii. "Eodentia." London 1848 (in- 

 cludes only the families Leporidm and Hystricidce). 



X Diet. Univ. d'Hist. Nat. si. p. 202 (1848) ; Ann. Scien. Nat. S"' s6r. t. «. 

 pp. 245, 246 (1853). 



§ Prod. Syst. Mamm. p. 91 (1811). 



