as 
1889.] ON PREPOLLEX AND PREHALLUX. 259 
4. On the Prepollex and Preehallux, with Observations on the 
Carpus of Theriodesmus phylarchus. By Prof. Karu 
BarDELEBEN (Jena). (Communicated by Prof. G. B. 
Howes, F.Z.S., F.L.8.) 
[Received April 30, 1889.] 
(Plate XXX.) 
In 1885 I gave the name “rudiments of preepollex and pre- 
hallux ” to those bones on the inner side of the carpus and tarsus of 
the Mammalia which were hitherto either quite unknown, or had 
been but briefly described as radial and tibial “‘sesamoids.’”’ 1 have 
found these bones in all orders of Mammals which have five functional 
digits. The “rudiment of the preepollex” (shortly called “ prae- 
pollex’’) is present in’ Marsupials, Edentata, Rodents, Insectivora, 
Carnivora, and Monkeys. The preepollex is situated on the trape- 
zium in Insectivora and Lemurs; between the scaphoid and the 
first metacarpal in Rodents and Carnivora; between the scaphoid 
and the trapezium in Monkeys. The prehallux articulates with the 
first cuneiforme in Marsupials, Insectivora, and some: Carnivora; 
with the same bone, or with the navicular, in Edentata and Rodents ; 
with both bones in other Carnivora; between the first cuneiform 
and the first metacarpal in Monkeys. The rudiments of the pre- 
pollex and preehallux are small, rounded, or elongated ossicles, often 
strikingly similar to a metacarpal or phalangeal bone. As almost 
all Mammals have also a supernumerary bone (formerly considered 
as a ‘‘sesamoid”’) on the oufer side of tie hand (pisiforme) and of 
the foot (tuberositas calcanei), I conclude (regarding these super- 
numerary elements as vestiges of reduced digits) that there are, in 
addition to the ordinarily recognized five digits, the rudiments of a 
sixth (internal) and of a seventh (external) digit, in both the hand 
and foot of Mammals. é 
I have also found a supernumerary cartilage on the tibial border of 
the tarsus in the human embryo of the second month; and Kehrer, 
a pupil of Wiedersheim, has shown (Berichte d. naturf. Gesellsch. 
zu Freiburg, Bd. i. Heft 4, 1886) that the Urodela have also 
rudiments of seven digits in embryonic stages. Consequently I was 
led to state, at the meeting of the German Naturalists and Physicians 
in Berlin (1886), that we must modify our former views on the 
pentadactyly of the higher vertebrates, inasmuch as we have ground 
for regarding certain cases of hyperdactyly (polydactyly), which are 
not unfrequently found in Mammals (more especially in the best- 
known Mammal, Man), as instances of atavism rather than of 
abnormality. 
Until this month I have neither had the time nor the requisite 
material for a more detailed inquiry into this important subject, 
nor had I seen the large collections of London and of North 
America. My intention to come to London has been on several 
