568 MR. ST. GEORGE MIVART ON THE [June 27, 
In Galago the manubrium is somewhat T-shaped, as in the skele- 
ton of G. allenii in the British Museum. 
The number of distinct bones posterior to the manubrium and 
anterior to the xiphoid cartilage varies, in the Primates below the 
Simiine, from four to six, except in Nycticebus. 
As to the number found in each genus, it is subject to some varia- 
tion. Thus in Semnopithecus and Colobus there are generally four 
in adults*, but sometimes five; in Cercopithecus almost always 
five, but rarely there are six even in adults; in Macacus and Cy- 
nocephalus five or six; in Afeles six, but in Cebus generally five,. 
and in the other Cebide and in Hapale four or five; the same in 
Galago, Indris, and Lemur, but in Loris and Perodicticus as many 
as six. In Nycticebus alone have I seen more than this, namely, as 
many as nine; but this was in an immature specimen. 
Riss. 
Almost all Primates have more true than false ribs. In the highest 
forms the number of pairs of true ribs is seven, but in Hylobates 
there are sometimes eight pairs. In Semnopithecus and Colobus 
there are generally seven, but sometimes eight pairs of true ribs. 
In the Cynopithecine the normal number is eight. In the Cebide 
there are generally seven or eight pairs, but in Ateles sometimes 
nine. In Hapale there are sometimes as few as six, sometimes as 
many as eight; seven or eight in Galago, Lemur, and Indris; nine 
in Chetromys. The highest number, as might be expected, is found 
in the Nycticebine, there being as many as ten pairs of true ribs in 
Perodicticust and Loris§. 
The total number of pairs of ribs is not always constant in the 
same species, there being in Man sometimes thirteen, sometimes only 
eleven pairs; in the Chimpanzee sometimes only twelve, and so on. 
The ribs of Man are distinguished from those of the other genera 
of the order by their more marked “ angles,’’ and by the greater 
arching backwards of their proximal parts. In these respects the 
Gibbons approach most nearly to Man. 
The remarkable sigmoid twist in a vertical direction, which exists 
in the ribs of Man, exists also markedly, though in a less degree, in 
Troglodytes. In Simia and the lower Primates it is much less no- 
ticeable. 
Pithecia\| is distinguished from all the rest of the order by the 
great relative breadth of the ribs, They are also wide, but to a less 
extent, in Hapale midas. 
In Man the ribs form a thorax which in its shape and proportions 
differs from that of all other forms of the order, it being half as 
broad again as it is vertically (¢. e. from back to breast) deep. 
* Tn an adult Colobus satanas in the British Museum (no. 1180 a) there are five. 
+ E.g.in @. ruber (no. 15g) in the British Museum. 
{ No. 745 in the British Museum. 
§ No. 4632 in the Museum of the Royal College of Surgeons. Noticed by 
Prof. Owen, ‘ Osteological Catalogue,’ vol. ii. p. 718. 
|| See the skeleton of this genus in the Museum of the Royal College of Surgeons, 
