ME. ST. GrEOEGE MIYAET ON THE SKELETON OF THE PKIMATES. 
123 
the length of the latter — which it is also, sometimes, in Hylobates. It has always more 
than half that proportion ( i . e. than one-twentieth), except in Chrysothrix, Loris, Nycti- 
pithecus, Arctocebus, Lemur, Perodicticus, and Colobus. In the last it is to the spine 
only as about 3'5 to 100. 
There is never a very large process on the palmar side of its proximal end, as there 
is so often in the corresponding part of the hallux. 
The proximal articular surface is sometimes concavo-convex, as in Man, the Gorilla, 
sometimes in the lower Simiidae and Cebidse, and in the Nycticebinse. But there is 
individual variation in this respect ; and often this double curvature is scarcely to be de- 
tected, e. g. in the Chimpanzee, Simia, Lemur, and Ateles. In Hylobates there is a con- 
cave surface only, which unites with the articular ball of the trapezium. 
The shaft of the bone generally broadens distally, but sometimes ( e . g. in some of the 
lower Simiidse) it tapers, yet never so much so as does the shaft of the hallux of the 
same species. 
The distal end is rarely broader than the proximal one, generally it is of almost the 
same width, but sometimes narrower. It is probably never so much broader in the 
forms below Man as it is in him. 
The angle formed by the transverse axis of the head with another similarly traversing 
the heads of the other metacarpals, always more or less nearly approaches a right angle, 
except in the Cebidse and Hapale, where it is more obtuse, yet not so much so as is 
the homotypal angle of the pes of Man. 
This metacarpal is never the longest one of the manus in any species, and it is the 
shortest one in all except the Nycticebinse (where it exceeds in length the second meta- 
carpal, and sometimes the fifth also) and Tarsius, where it slightly exceeds the fifth, 
but not the second one *. 
Second Metacarpal . — ‘This is sometimes the absolutely shortest metacarpal found in 
the whole order ; namely, in Arctocebus. It is the longest of all in the same manus in 
Man, sometimes in Troglodytes and Simia, in Hylobates, and in the Cynopithecinse. 
It is the shortest one in the Nycticcbinse. It is shorter than the three metacarpals 
external to it in Indris, Cheiromys, and, of course, in the Nycticebinse. 
Its proportion to the metacarpal of the pollex is greatest in the Chimpanzee, where 
it is more than twice and a half its length, then in the Semnopithecinee and the 
Gorilla. In all the rest it is longer than the metacarpal of the pollex, except in the 
Nycticebinse, where, in Arctocebus, it is scarcely more than three-fourths its length. 
The metacarpal of the index projects furthest (distad) of any in the same manus, 
in Man, sometimes in Troglodytes, in Hylobates, and sometimes in the lower 
Simiidse. 
It projects distad less than do the three metacarpals external to it in some, e. g. 
in Ateles, Pithecia, and sometimes Hapale, the Lemuridse, and Cheiromys. 
In Indris the shaft is much curved, with the concavity radiad. 
* See Bhraietster and Blanchard, Joe. cit. 
2 Y 
MDCCCLXVII. 
