546 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
Baur,’ as the result of his investigations of the reptilian carpus, con- 
cluded that the preepollex element was one of the true carpals (radiale) 
displaced, being pressed out whilst the radiale centrale had taken its 
place and appeared as the representative of the true radiale. He con- 
siders that a similar view may be held regarding the amphibian carpus. 
Baur thus questions the validity of the prapollex theory. On the other 
hand, Bardeleben* is. one of the strongest exponents of the theory. 
After studying the subject from the embryological standpoint and 
examining more than a thousand skeletons in the comparative anatomy 
collections of Berlin, Leyden, and London, he concludes that we must 
relinquish the old doctrine of five digits for the mammalia. The argu- 
ment of Bardeleben is very interesting and ingenious. He finds in one 
of the Cape rodents (Pedetes capensis) in two skeletons a przpollex 
possessing a nail, and a postminimus in which were two bones. He also 
conducted his investigations among fossil forms and in the oldest 
fossil mammal in which the hand skeleton has been preserved he 
describes a preepollex rudiment. This fossil animal 7hertodesmus phy- 
larchus, comes also from South Africa (Nicholson*). The prapollex 
rudiment in the carpus of Theriodesmus has also been described by 
Thilenius.*| The elements of the prapollex rudiment here, according 
to this authority, lie on the radial side of the hand, between the scaph- 
oid, centrale and trapezium. Bardeleben, in his paper, attempts to trace 
the muscles of the prapollex and the post minimus, or rather their repre- 
sentatives, in the pentadactyle type. Thus the palmaris longus in the 
hand, and the plantaris in the foot, are looked upon as giving evidence. 
of the existence of those supernumerary digits. Among lower animals 
(as has already been stated for the palmaris longus) these muscles give 
a varying number of tendons, numbering from three or four to seven, 
in some animals. Thus Bardeleben states that we have seven tendons 
representing the termination of the muscle in Cenfetfes (one of the 
hedge-hog family of Madagascar). One of these tendons went to the 
prepollex and the other to the postminimus. Similar conditions were 
found in the plantaris. To the four groups of interossei present in the 
mammalian hand or foot Bardeleben would add the abductor muscles 
1 G. Baur, ‘‘Der Carpus der Schildkréten.’ Anatomischer Anzeiger, 1892, p. 206. 
2 K. Bardeleben, ‘‘ Ueber die Hand-und Fuss-Muskeln der Sdugetiere, besonders die des Przepollex 
(Przhallux) und Postminimus,” Anatomischer Anzeiger, 1890, p. 435- 
3 A. Nicholson, ‘‘A Manual of Palzontology.”’ Edin, and Lond., 1889. Vol. IJ, p. 1269. Nicholson's 
description of this mammal is as follows :—‘‘In the Karoo system of South Africa, in a horizon which is 
probably of lower mesozoic age, has been obtained a slab showing the impression of a pectoral limb, appar- 
ently referable to a small mammal, which has been described under the name of Theriodesmus.” 
4 G, Thilenius, ‘‘ Ueber Sesambeine fossiler Sdugetiere,”” Anatomischer Anzeiger, 1894-95, p. 42. 
