9() INDEX GENERUM MAMMALIUM. 
In a few instances genera have been defined without mention of any 
specles, but fortunately such cases are extremely rare in mammalogy. 
Examples may be found in Amblysomus Pomel, 1848, and Chalco- 
chloris’ Mivart, 1867, two names for a subgenus of South African 
golden moles. No species were mentioned in the original descriptions, 
and no specific names seem to have been coupled with Amblysomus 
until 1879? and none with CAafcocAloris until 1882. 
The term type’ as now understood was unknown a century ago, and 
the importance of designating some one species on which the descrip- 
tion of the group had been based was not appreciated by the older 
naturalists. A genus may contain ten or more species which subse- 
quently are found to represent as many different genera or subgenera. 
Under such circumstances it becomes of the utmost importance to 
determine which one should bear the name of the original group. To 
determine this point 1s often an exceedingly difficult matter and in 
complicated cases can only be settled after a full consideration of the 
facts by one who is engaged in monographing the group or who is 
thoroughly familiar with the history of the species involved. 
As Dr. Dall has well said, ** No arbitrary rule will suffice to deter- 
mine, offhand, questions of so much complication as is often the 
decision in regard to the type of an ancient genus which has been 
studied by a number of authors." 
To meet the difficulties which frequently arise several methods of 
procedure have been proposed. The most important of these are: 
(1) Selection of the first species. 
(2) The species selected by the first reviser of the group. 
(3) The species, if any, whose name has subsequently become the 
designation of a genus. 
(4) Elimination (especially as restricted by Canon XXIII of the 
A. O. U. Code). 
“Originally spelled Calcochloris. 
> Trouessart, Revue et Mag. Zool., 3° ser., VII, 277, 1879. 
^ À type is the identical individual specimen from which a species has been de- 
scribed. To meet the demands of modern systematists Thomas has proposed the 
following terms for specimens more or less closely associated with the original type: 
Cotype: “One of two or more specimens together forming the basis of a species, no 
type having been selected.’’ 
Paratype: “A specimen belonging to the original series, but not the type, in cases 
where the author has himself selected a type." 
Topotype: ** ^ specimen simply collected at the exact locality where the original 
type was obtained.’ 
Metatype: “A specimen received from the original locality after the description 
has been published, but determined as belonging to his own species by the original 
describer himself." —Proc. Zool. Soc. London, 1893, 242. 
See also Schuchert, * What is a Type in Natural History?', Science, new ser., V, 
636-640, Apr. 23, 1897; and Merriam, Ibid, pp. 731-732, May 7, 1897. 
“Nomenclature in Zoology and Botany, Rept. to the Am. Ass. Adv. Sci., p. 40, 
1877. 
