456 Mr. O. Thomas on 
monkeys * has had an unfortunate effect so far as nomen- 
clature is concerned owing to its very excellence, for later 
authors have accepted his names, new or old, without en- 
quiry, with results that now prove to need much revision. 
Firstly, Callithriz, quoted quite commonly as from this 
paper, and consequently used for the Titis, was really first 
founded in 1777 by Erxleben, who included in it six monkeys, 
no one of which was a Titi; and it is therefore quite evident 
that some other name must be used for this group. ‘Thanks 
to the labours of Lesson, Gray, and others, names are nume- 
rous among South-American monkeys, but, curiously enough, 
I can find none that has ever been applied to the Titis except 
this untenable Callithriz and the misapplied “ Saguinus, 
Lacépéde,” of Lesson, whose real basis was the common 
marmoset. 
The Titi Monkeys will therefore need a new name, and 
Callicebus may be suggested for them, with C. personatus, 
Geoff., as the type species. 
Passing to the Marmosets, we find that authors have been 
contented to use Illiger’s Hapale of 1811 for them, ignoring 
the fact that no less than three earlier names exist, namely: 
Callithriz, Erxleben, 1777; Sagoinus, Kerr, 1792; and 
Sagouin, Lacépéde, 1799. 
Callithriz, Krxleben, contains six species— C. pithecia and 
five Marmosets. ‘The first-named of these was made the 
type of the genus Pithecia by Geoffroy in 1812, now there- 
fore Pithecia pithecia, leaving the type to be found among 
the Marmosets. Fortunately this can be definitely fixed by 
the quctation of “ Callithrix” as the first synonym of Call- 
thriz jacchus, this species having therefore to be taken as the 
type under the rule recently published on the subject in 
‘Science’ fT. 
In the splitting of the Marmosets into two genera this 
allocation of the type is fortunate, for it makes Jacchus, Geoff. 
(type C. jacchus), a pure synonym of Calithriz, and leaves 
Midas, Geoff. (type M1. midas), available for the ‘ ‘Tamarins,” 
the Marmosets with long typically-formed lower canines and 
small incisors, the group to which the name has usually been 
applied. 
Sagoinus, Kerr, 1792, containing exactly the same species 
as Erxleben’s Callithriz, becomes a full synonym of it, and 
cannot be used for any part of the group. The name being 
* “Tableau des Quadrumanes,” Ann, Mus. xix, p. 85 (1812). 
+ ‘Science,’ xvi. p. 114°(1902). 
