27 
4b. Recommendation. — It is well to avoid the introduction of the names typicus 
or typus as new names for species or subspecies, since such names are always liable 
to result in later confusion. 
5. Rule. — If a genus, without designated type, contains among its original species 
one possessing the generic name as its specific or subspecific name, either as valid 
name or synonym, that species or subspecies becomes ipso facto type of the genus. 
(Type by absolute tautonymy.) 
6. Recommendation. — If a genus, without designated type, contains among its 
original species one possessing as specific or subspecific name, either as valid name 
or as synonym, a name which is virtually the same as the generic name, or of the 
same origin or same meaning, preference should be shown to that species in desig- 
nating the type, unless such preference is strongly contraindicated by other factors. 
(Type by virtual tautonymy.) 
7. Rule. — In case a generic name without designated type is proposed as a sub- 
stitute for another generic name, with or without type, the type of either when 
established becomes ipso facto type of the other. 
8. Rule. — If an author proposes a genus, without designating a type, and includes 
among the original species [i. e., the valid species from his standpoint] the deter- 
mined type of an earlier genus, such type becomes ipso facto the type of the new 
genus. (Type by inclusion.) 
9. Rule. — If a genus without a designated type contains types of two or more 
earlier genera, the type of the new genu- is to be selected from the contained types 
(the case being the same as a genus with two or more species, according to the num- 
ber of types in question), unless it can be shown that such procedure is directly 
contraindicated by the original author’s intentions. 
10. Rule. — If an author, in publishing a genus with more than one valid species, 
fails to designate or to indicate its type, any subsequent author may select the type, 
and such designation is not subject to change. (Type by subsequent designation.) 
11. Rule. — Certain biological groups which have been distinctly proposed as 
collective groups, but not as systematic units of generic rank, may be treated for 
convenience as if they were genera, but they require no type species. Example: 
Agamod istomu m. 
12a. Rule. — The following species are excluded from consideration in selecting 
the types of genera: 
(a) Species which were not included under the generic name at the time of its 
original publication. 
(h) Species which were species inquirendse from the standpoint of the author of 
the generic name at the time of its publication. 
(c) Species which the author of the genus doubtfully referred to it. 
(d) Species which have subsequently been selected to serve as types for other 
genera, unless this applies to all of the available species, in which case the last species 
so selected becomes the type of the original genus; or unless the species which the 
original author took as his type has been transferred, in which case the original 
author’s intentions should be carried out. (Type by elimination.) 
12b. Rule. — In case of Linntean genera select as type the most common or the 
medicinal species. (Linntean rule.) 
12c. Recommendation. — The following species should be shown preference in 
selecting the type, unless such procedure is contraindicated by the original author’s 
intentions or by practical considerations: 
(а) If the genus contains both exotic and nonexotic species from the standpoint 
of the original author, the type should be selected from the nonexotic species. 
(б) If some of the original species have later been classified in other genera, but 
not designated as their types, preference should be shown to the species still remain- 
ing in the original genus. 
