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 seme of the more 

 interesting facts which I have established. 



In some Mammals (for example, in Pedetes capensis) the prse- 

 pollex consists of two bones (Plate XXX. fig. 2), of which, in a 

 si)ecimen in the British Museum, the proximal {Pp.p.)is 13 miUim. 

 long, and the distal (Pp.d.) 7 millim. And, above all, this rudiment 

 of a digit bears, in this animal, a genuine naiP ; whereas many true 

 digits, such as the halluxes of Marsupials, are without nails. The 

 prsepollex 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 Hathyergus viaritimus (Plate XXX. fig. 3) the prsepollex 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 (jn.d.) is 7'5 millim. 

 in length. We must therefore in the future distinguish a proximal 

 I'rom 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 

 a digit. 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 praepollex and prsehallux are digits too, at least in the 

 cases of Pedetes, Talpa, and many others. Everybody who has 



' Mr. Oldfield Thomas, to whom I had shown the two bones in the pras- 

 polle.x, examined for me the skins of this animal which are jJi'eserved in the 

 collection, and found the nail in question. Piof. Howes has since informed 

 me that a similar, but less specialized, eornificatiou overlies the immense jprse- 

 hallux of Ccrcolabcs (C. novm-hispania). 



