MUPJDAE—SIGMODONTES— HESPEROMYS LEUCOPUS. 



73 



Table XV. — Measurements of twelve specimens purporting to he Hesperomys "austerus". 



* This specimen is remarkably blackish, with very puro white feet, and seon by itself would readily suggest a 

 distinction of species from ordinary leucopus. It is the extremo of tho "austerus " style. 



This little table is curious and suggestive. The twelve specimens happen 

 to differ among themselves in size and proportions nearly as much as the 

 whole eastern series of leucopus does, and show more variation than would 

 be required to establish several distinct species upon the slight basis that has 

 been often employed. And after allowing a wide margin for chances of error 

 in measurement (always a safe thing to do in dealing with stuffed skins of 

 small mammals), discrepancies remain that cannot be explained away. The tail 

 varies an inch, and the ears and feet are quite as variable. To sum up (with 

 special reference to "boylii", that we are about to discuss): The tail, com- 

 pared with the trunk, ranges from less than the average of eastern leucopus 

 up to nearly the average of "myoides" or "boylii". The ears range from the 

 smallest of leucopus to the largest of "boylii". The feet have the ordinary 

 range of either leucopus or "boylii". Nothing further is needed to prove our 

 point. 



In analyzing our species of Hesperomys, Professor Baird put "myoides" 

 and "boylii" together, because they agreed in a length of tail exceeding the 

 average of true leucopus. Of "boylii" he says : — "No cheek-pouches 1 Tail 

 three-quarters of an inch longer than the [head and] body"; and of "myo- 

 ides": — "With cheek-pouches. Tail a quarter of an inch longer than the head 

 and body." The supposed distinctions of color do not hold ; for No. 1313 

 ("myoides", Burlington, Vt.) and No. 578 (" boylii", Shoalwater Bay) are almost 

 precisely alike in color — much more so than two specimens of "boylii" (No. 

 578 and No. 356, for example) are. No. 356, the type of "boylii", is the very 



