36 Zoology of Colorado 



RODENTIA 



The rodents are the most successful mammals, if success is 

 measured by the number of genera, species and individuals. 

 Colorado is the home of a great variety of these animals, always 

 easily distinguished from other orders by the teeth. The total 

 absence of canine teeth shows them to be an end group, not 

 leading to any other. Twenty-eight species and subspecies of 

 rodents have been described as new from Colorado specimens. 

 Of these, three were published in 1823, one in 1852, three in 1855, 

 and one in 1857. These dates belong to the periods of Say and 

 Baird. Next follows an interval of over 30 years, when no 

 additions were made. When the writer came to Colorado in 

 1887, it was supposed that the rodents were well known, and I 

 had no idea of the long series of discoveries which the future would 

 reveal. But a new Colorado form was described in 1890, one in 

 1891, three each in 1893 and 1894, one in 1897, one in 1899, one 

 in 1905, one in 1907, three in 1908, one in 1909, and one each in 

 1912, 1914, 1915 and 1918. It must be explained that the large 

 number of additions is due to the refinements of modern mam- 

 malogy. Not only have good series of specimens been collected, 

 but the analysis of these materials has been much more thorough. 

 The modern period may be called the Merriamian, for it was Dr. 

 H. C. Merriam who was mainly responsible for initiating the new 

 methods. Europeans were at first scornful, but at length came 

 to appreciate what was being done. Consequently, arrangements 

 were made for G. S. Miller of the U. S. National Museum to go to 

 England, and prepare for the British Museum a work of over a 

 thousand pages describing the mammals of Western Europe. 

 This work, certainly one of the classics of zoology, employs the 

 same methods of minute analysis which had become customary 

 in America. 



The characters employed in all this work have been the 

 external features of form and color, and the skulls and teeth. 

 There is very much more to be done, on the various skeletal 

 features, the auditory ossicles, and the numerous characters of the 

 soft anatomy. In 1913 a study of the intestines of Colorado 

 rodents was published.* It was recorded that the absolute and 



*Ccckerell, Miller and Printz, The Relative Lengths of the Large and Small Intestines in 

 Rodents; Proc. Biol. Society of Washington, Dec. 20, 1913. 



