320 Monograph of the Genus Semnopithecus. 



Art. IV. A Monograph of the Genus Semnopithecus. By W. C. 

 L. Martin, Esq. F.L.S. &c. 



The genus Semnopithecus, established by Fred. Cuvier, con- 

 tains a group of Simiadce exclusively restricted to India and 

 its islands. As respects external characters, the members of 

 this genus differ, in many essential points, from the Cercopi- 

 theci of Africa, insomuch that a glance is sufficient to enable 

 us to discriminate between them. Nor is it only in external 

 characters that this difference exists; it obtains to a most re- 

 markable degree in the structure of the digestive organs, as 

 will be pointed out hereafter, proving that the alliance between 

 these genera, is less immediate than might at first have been 

 imagined. In many respects, indeed, the Semnopitheci ap- 

 proximate towards the gibbons, especially in dentition, and 

 contour of body. Like the gibbons, {Hylobates), and the ma- 

 caques, (Macacus), the Semnopitheci have five instead of four 

 tubercles on the crown of the last molar tooth of the lower 

 jaw. The body is slender, the limbs long and thin, as are 

 also the hands and feet ; cheek-pouches are either wanting, 

 or very small, but there is a large laryngeal sac, communi- 

 cating with the larynx ; the callosities are small ; the tail is 

 of great length. In the gibbons, there is as in the Semnopi- 

 theci, a laryngeal sac, and small callosities ; in the former a- 

 nimals however, it is in the arms that we find so remarkable 

 a degree of length, and not in the posterior extremities, which 

 are indeed short in proportion. In the Semnopitheci on the 

 contrary, the hinder limbs are even more strikingly developed 

 than are the anterior, and with this developement of the hind- 

 er limbs is associated a long and slender tail, acting as a ba- 

 lance in all their movements. The rounded form of the skull, 

 the developement of the forehead, and the obtuseness of the 

 facial angle, are marked characters in the gibbons; the Sem- 

 nopitheci, while young, exhibit these peculiarities also, but 

 as they attain to maturity, the muzzle advances and the fore- 

 head recedes, becoming apparently diminished also in its ad- 

 measurements, so that the facial angle, instead of continuing 

 at about 60°, is reduced to 40° or 45°. The supra-orbital 

 ridge is by no means prominent, but it is surmounted by a 

 row of long bristly hairs, projecting forward, and forming a 

 sort of continuous eyebrow, more full in some species than in 

 others. In indicating the points of structure in which the 

 Semnopitheci approach the gibbons, we do not mean to say 

 that the species of the one genus can by any possibility be 

 assigned to the other genus, — the gibbons are too well defin- 

 ed a group, and have characters too clear to be mistaken, even 



