the Genera of Hapalide. 257 
so far as I am aware, there is no evidence that this area 
becomes bald even in extreme old age. ‘The condition 
presented by this species, indeed, lessens the value—small in 
any case—of the characters upon which Seniocebus was based ; 
and if Elliot had not unconsciously evaded the difficulty by 
placing leucopus in a wrong genus, he would probably have 
been puzzled in deciding whether it should be located under 
Seniocebus or Cercopithecus or Leontocebus, in the sense in 
which he used those terms, because the species is intermediate 
between Seniocebus and the others, according to Hlliot’s 
definition of that genus. 
Elliot quoted Zamarin, Gray, as a synonym of Seniocebus. 
This is an unintelligible error, because ZYamarin, Gray, 
included only midas and ursulus, the two species to which 
Elliot restricted the name Cercopithecus. Yamarin, there- 
fore, should have figured amongst the synonyms of Cerco- 
pithecus. Moreover, since Tamarin has line priority- over 
Seniocebus, the former should have been adopted by Elliot, 
with Senzcebus as the synonym, if, as he stated, the two 
names had been applied to the same group of species. 
Genus HApALg, Illig. 
Callithriz, Erxl. Syst. Régn. Anim. 1777, p. 55; type jacchus, Linn.* 
Hapale, Mlig. Prodr, Syst. Mamm. p. 71 (1811); type jacchus. 
This genus contains many species broadly resembling Vystax 
in the structure of the hands and feet, and apparently also of 
the ears, but differing from Mystaz, as from the other genera 
of the family, in the well-known modification of the anterior 
mandibular teeth described by Gray and others ; the incisors 
are abnormally long, and form a continuous or nearly con- 
tinuous series with the canines, which they approximately 
equal in height and thickness. This modification is accom- 
panied by a more or less marked compression and recession 
of the chin. Although these characters are subject to a 
certain amount of specific and possibly individual variation, 
I have seen no skulls of Hapale which could not be at once: 
identified as belonging to that genus. 
* I see no reason to interfere with the synonymy of this genus as 
published by Elliot. I have only been able to examine in the fresh state 
one species—namely, jacchus, the common white-eared marmozet, with 
which the black-eared form, quoted as penicil/atus and given full specific 
status by Elliot, completely intergrades. Jacchus may be taken as the 
type of Sagoninus, Kerr, Hapaile, Illig., Jacchus, Geoftr., Arctopithecus, 
Virey, Ouwastitis, Burnett, and Liocephalus, Wagn. Generic synonyms 
with other type-species are :—Mzico, Lesson, type argentatus; Micoella, 
Gray, type sericea (=chrysoleuca) ; Cebuella, Gray, type pygmea. 
