1891. ]} NEW YORK ACADEMY OF SCIENCES. 83 
added during the last six years, nearly doubling the number re- 
cognized in 1877. 
Of the squirrels, Baird admitted thirty-nine species —an 
enormous reduction, by the way, from the number recognized 
by Audubon and Bachman. In 1877 I confirmed Baird’s pre- 
vious reductions, and still further reduced the number to thirty- 
three species and subspecies, adding, however, eight to those 
recognized by Baird. Since 1877 a large number of species 
and subspecies has been added, mainly among the ground squir- 
rels and spermophiles. ‘These additions are based on almost 
wholly new materials, and include species as distinct from their 
nearest allies as any previously known. ‘That is, they are not 
the result of a new way of looking at things, but are actual dis- 
coveries of forms not at all closely related to anything known 
before. 
Of the Saccomyide, Baird in 1857 recognized nine species; 
Coues, in 1877, admitted the same number. This group dur- 
ing the last four years has been thoroughly revolutionized, 
mainly by Dr. Merriam.’ The names of several of the old 
species have been shown to have been strangely misapplied; one 
new genus and a new subgenus, and some twenty or more new 
species, have been added, besides numerous subspecies. Among 
the new forms are some strikingly different from any known to 
either Baird or Coues, while others differ in only comparatively 
slight particulars. These animals are peculiar to the arid plains 
and deserts of the West; are nocturnal] and somewhat subterranean 
in their habits, and seem, moreover, especially susceptible to the 
influence of conditions of environment. Owing totheir peculiar 
habits, and to the fact that the area they inhabit has been, till 
lately, little explored, very few specimens were extant in collec- 
tions up to a very recent date. 
Of the Leporide, or hares, Baird in 1857 was able to recognize- 
but thirteen species as North American. All but one of these 
were admitted by me in 1877 and two others were added. Within 
the last year five others have been recognized, three of which are 
very distinct from any previously known, while two are old ones 
revived as subspecies. 
To what, then, is all this change due ? ‘To several very ob- 
vious causes. First, toa vast increase of material; second, to its 
greatly improved quality; third, to more thorough and intelli- 
gent work in the field, conducted on a tenfold greater scale 
than ever before. Thousands of specimens are taken now where 
formerly only a few scores were obtained. Collecting and all 
1«* North American Fauna,” No. 1, Oct., 1889; ibid., No. 3, Sept., 1890, 
pp. 71-75; and ibid., No. 4, Oct., 1890, pp. 41-49. 
