260 PROF. KARL BARDELEBEN ON [May 7, 
occasions frustrated. In the meantime, many observations agreeing 
with my own have been recorded by other authors ; and there has 
been a strong attack made upon my views by Prof. Gegenbaur 
(Morphol. Jahrbuch, vol. xiv. p. 394, 1888). 
This attack, emanating from one of the most celebrated com- 
parative anatomists of the day, impelled me to renew my investiga- 
tions on the subject and, for this purpose, to study the collections 
preserved in the British Museum, where I have found both a very 
large amount of material and have met with the greatest kindness in 
helping me to use it. Of those to whom I am particularly indebted, 
I may mention Prof. Flower, Dr. Giinther, Dr. Woodward, Mr. 
Boulenger, Mr. Lydekker, and especially Mr. Oldfield Thomas, who 
allowed me to work in his room, and who gave me much assistance 
in my examination of the Museum specimens. 
These recent observations have fully corroborated my previous 
conclusions on the subject. Although it is not possible for me 
just now to communicate all the results I have obtained in London, 
I may nevertheless give a short account of some of the more 
interesting facts which I have established. 
In some Mammals (for example, in Pedetes capensis) the pree- 
pollex consists of two bones (Plate XXX. fig. 2), of which, in a 
specimen in the British Museum, the proximal (Pp.p.)is 13 millim. 
long, and the distal (Pp.d.) 7 millim. And, above all, this rudiment 
of a digit bears, in this animal, a genuine nail’ ; whereas many true 
digits, such as the halluxes of Marsupials, are without nails. The 
preepollex of Pedetes is very large, and the nail is a true one, singu- 
larly like that of the human thumb and similarly longitudinally 
striate (Plate XXX. fig. 1). 
In Bathyergus maritimus (Plate XXX. fig. 3) the preepollex and 
the postminimus are both very well developed. The latter consists of 
two bones, of which the proximal (pi.p.) is the true pisiform and 
measures 5 millim. in length, while the distal (pi.d.) is 7°5 millim. 
in length. We must therefore in the future distinguish a proximal 
from a distal “ pisiform ;”’ and I regard the former as, in all proba- 
bility, the carpal, and the latter as the metacarpal segnient of the 
postminimus. 
If, with the carpus or tarsus of an animal with five digits, there 
articulate one or two supernumerary bones having the form and 
relationships of those ordinarily representing a reduced pollex or 
hallux, we have good reason for regarding the same as rudiments of 
adigit. It is most difficult, however, to say wherein a digit consists. 
How many bones must it contain? Is the mammalian thumb 
invariably a complete digit, or is it only a rudiment? If it is a 
digit, the preepollex and preehallux are digits too, at least in the 
cases of Pedetes, Talpa, and many others. Everybody who has 
1 Mr. Oldfield Thomas, to whom I had shown the two bones in the pre- 
pollex, examined for me the skins of this animal which are preserved in the 
collection, and found the nail in question. Prof. Howes has since informed 
me that a similar, but less specialized, cornification overlies the immense pra- 
hallux of Cercolabes (C. nove-hispani@). 
