CFIRONOLOGICAL CATALOGUE. 43 



1857. Baird, SrENCER F. — Contiuued. 



"The column of 'original numbers' ombracea those attached to apeclmens in the field by- 

 collectors. These arc alwaj's retained as being referred to in the fleld-notea of the different 

 parties. 



" The measurements have, in all cases, been made in English inches,* divided either into 

 lines or tweKths or into one-hiindredths. All the skulls, and in most cases the smaller skins, 

 have been measured with dividers or callipers. The measurements of the body have been 

 made to the insertion of the tail into the rump, or nearly to the very base of the caudal ver- 

 tebra; ; the animal usually with the head, body, and tail extended into the same straight line, 

 avoiding, as far as possible, all curvature. 



" Where measurements are recorded as made before skinning, they are, in most cases, to 

 be understood as having been furnished by the collector. 



" Por the sake of illustrating more fidly the character of the species described in the pres- 

 ent report, I have preiiarod the three lists as follows : 



" The tirst list is that of the higher groups characterized in the following pages. 



"The second list contains all the species of mammals, found in North America north of 

 Mexico, that I have had an opportunity of examining while preparing the present work, to- 

 gether with a few that belong to the northern provinces of the last-mentioned State. These 

 are inserted as very probably existing within the limits of the United States, even though 

 not yet detected. The indications of geogi'aphic.al distribution arc chiefly those furnished by 

 the specimens before me, although I have occasionally given statements in this respect from 

 Audubon, Bachman, and Richardson. I have not pretended to define with critical accuracy 

 the complete range of the species, the facts on record not being sufficient for the purpose. 



"The third list embraces the species which have not fallen under my notice. Some of these 

 have little claim to a place in the fauna of North America north of Mexico, while others are, 

 in all probability, the same as those mentioned iu the first list. A few are unquestionably 

 additional and good species, especially such as Sorex fimbripes and palustrig, Putorius ni- 

 gripes, Arctomys pruinosus, Thomomys talpoides? Arvicola borealis, drummondii, riehard- 

 sonii, SLJid. xanthogiiathus, and some others. 



" The following table will serve to indicate the additions in the list to the known species 

 of North American mammals, as compared with the latest general work on the subject: 



Species described here as new for the first time 35 



Species described in 1855, from the same collection 17 



Total of new species in the Smithsonian collection not mentioned by Audubon and 

 Bachman 52 



Recognized species previously described, not mentioned by Audubon and Bachman 18 



Total of North American species additional to the list of Audubon and Bachman. . 70 

 " The entire number of species mentioned by Audubon and Bachman iu the Quadrupeds 

 of North America, exclusive of varieties, is 197, of which about 160 were figured, the re- 

 mainder consisting either of species previously described by the authors, but not procurable 

 for purposes of illustration, or else copied from others, to render their work complete, 



" The total number of species of North American mammals represented in the Smithsonian 

 collection is very nearly 220. Washington, D. C, July 2U, 1857." < Extracts from {Preface) 

 Exploration and Survey for the Pacific R. R., vol. viii, 1853-6, pp. xxv, xxvi, xxvii, xxviii, and 

 xxix. 



"GENERAL SKETCH OF USES EXPLORED. 



"Shortly before the close of the session of Congress in March, 1853, nn appropriation of 

 $150,000 was made to defray the expenses of the survey of the various routes along which it 

 was supposed that a railroad might be constructed from the Mississippi River to the Pacific 

 Ocean. For this purpose six parties ^vere organized by the War Department for the survey 

 of four main routes, and in a short space of time they were in the field. All the parties were 

 fitted out in the most complete manner ; the natural-history apparatus and material prepared 

 under the direction of the Smithsonian Institution, which also furnished the necessary in- 

 structions as to the objects most important to be collected. In its efforts to secure the assign- 

 ment to these parties of persons capable of making collections and observations it was met 

 by the hearty co-operation of the War Department, through the heads of the different 

 expeditions and Captain Humphreys, in charge of the Pacific Railroad office. 



"A more detailed account of the collections and expeditions referred to above will be found 

 in the Reports of the Smithsonian Institution— (sixth to the eleventh, 1851-1856). A notice 



* The English inch used is about equal to 11.26 French lines, .9383 French inches, or to 25.40 

 millimeters. On the other hand, the French inch is equal to 1.0657 English inches, the 

 French line to .0888 English inches, and the millimeter to .03937 English inches. The French 

 meter is equivalent to 39.37 English inches, or 3.28 feet. 



