98 UNGULATA. 
in size, and sooner or later are fused with the frontals! This strange outgrowth of the 
frontal bones has been verified on four adults; and consequently the natural suggestion 
that it was a monstrous individual feature is rendered improbable. The first premolars 
of the Guatemalan form, in comparison with those of #. bairdi, are in the upper jaw 
much narrower and divided into halves, the anterior of which is compressed and of 
almost uniform width, while the inner face of the posterior half bulges abruptly 
inwards; in the lower jaw they are also narrower, and the anterior cusp is separated by 
a vertical groove on the inner face of the tooth”. 
As far asI am aware, the full description promised by Dr. Gill has never appeared, 
and the above notes are so brief and indefinite that it is difficult to appreciate the value 
of the characters indicated. On making application to my kind correspondent, Pro- 
fessor Spencer F. Baird, I was last year intrusted with one of the typical skulls, and 
Dr. Gill was so good as to supervise the execution of drawings of the fronto-nasal region 
in two others of the series. Iam indebted to Professor Alphonse Milne-Edwards for a 
careful sketch of a skull in the Paris Museum; and I found a large series of Central- — 
American Tapir-skulls in the British Museum, the Museum of the Royal College of 
Surgeons, and in the collection of Mr. E. Gerrard, jun. In examining this material I 
had the benefit of the assistance of Professor Flower, Dr. Giinther, and Mr. Sclater ; 
and the result is the conviction that the characters of 7. dow& drawn from the fronto- 
nasal region, are constant and very remarkable, while those founded on differences of 
dentition cannot be depended upon. As these former peculiarities have never been 
properly figured or fully described, and as some of them are unique, I believe, in the 
Mammalian class, I will here enter more into osteological detail than has been thought 
advisable in the rest of the present work. 
The comparison of a sufficient series of skulls in any species of Tapir shows the 
existence of a very remarkable extent of individual variation in minor dental and cranial 
characters; and I have not found any of the differences pointed out by Dr. Gill as 
distinguishing 7. dow? from T. bairdi to be constant, except the extraordinary modifica- 
tion of the fronto-nasal region, which will be best understood by a comparison of the 
following descriptions with the figures on Pl. VIII. 
In T. bairdi, as shown in figs. 1 and 2, the nasals are well-developed bones at all ages, 
having a considerable thickness at their base, and, consequently, articulating with the 
frontals by a comparatively large surface. They are considerably longer, in the adult, 
than their united breadth, and they form the greater portion (in some examples the 
whole) of the characteristic pits which lodge the basal sinuses of the nostrils. In some 
specimens the frontals show a slight projection between the bases of the nasals, but the 
latter may always be said to articulate with one another throughout the greater part of 
their length. When we turn to the known skulls of 7. dowi we find a very different 
arrangement of these parts. 
* Amer, Journ. Science, 1. pp. 141, 142. 
