Correspondence—Ur. C. Davies Sherborn. 573 
their development, have had no need of passing by the stage of 
Hipparion to arrive at Equus; their evolution in this direction has 
given the form of the teeth of Meryhippus, Protohippus and Equus, in 
the proper sense of the name; and in this chain, it has not been 
necessary for any of the essential parts of the molars to disappear in 
order to re-appear later, or to develop parts completely new and 
different.” Hipparion, indeed, is to be looked upon as “a form 
which became separated from the direct Equine series before the 
evolution of the Aquus-type was complete, and perhaps even before 
Anchitherium aurelianense.” 
A study of the milk-teeth of the successive genera supposed to be 
ancestral to the Horse seems to lead to at least three conclusions, as 
follow : —‘* 1. The milk-molars are not a repetition of the premolars 
of the preceding form, but, on the contrary, foreshadow the premolars 
of a new form which is to follow; 2. The difference between the 
milk-teeth and the premolars of one and the same form is greater in 
proportion to its antiquity ; 3. The resemblance between the milk- 
teeth and the premolars in two successive forms is closer in propor- 
tion to their antiquity.” 
A table showing the known geographical and geological distribu- 
tion, with the supposed relationships, of the several Equine genera is 
appended ; and Madame Pavlow promises to supplement the work 
shortly by a memoir upon the Pleistocene horses of Russia. 
The section (III.) upon the Rhinocer[ot ide and Tapiride is 
mainly a synopsis of the literature of the subject; and this appears 
to show that Systemodon, of the North American Eocene, is an 
immediate predecessor of the families under discussion, while 
Hyrachyus also is a missing link. AC Saas 
CORRESPONDENCE. 
ee a 
A PLEA FOR A UNIFORM SYSTEM OF ABBREVIATION WHEN 
QUOTING SCIENTIFIC PERIODICALS. 
Str,—It would be not only a great convenience to scientific 
students in general, but a much more satisfactory proof of the 
acquaintance of an author with the book he refers to, if some 
uniform system of abbreviation were adopted when quoting 
scientific literature. It is exceedingly perplexing to find variants 
in the abbreviation of a book-title, and has often caused consider- 
able trouble and annoyance to those coming across them for the first 
time. A few years ago writers had some excuse for these and 
similar carelessnesses, inasmuch as no list of abbreviations had then 
been published, but when in 1874 W. Whitaker and W. H. Dalton 
issued the first volume of the Geological Record, they gave an 
excellent list of abbreviated titles, supplying the want of a book 
of reference, and leaving no excuse for “sloppy” quotation. 
This list has been further enlarged and improved in the volume for 
1880-84, just issued, and may be taken, with very few exceptions,! 
as an absolutely safe set of abbreviations, each being distinct and 
' It is always advisable to quote the p/ace of publication in full in a scientific title. 
