8 BUREAU OF ANIMAL INDUSTRY. 



3. RULE. When in the original publication of a genus one of the species is 

 definitely designated as type, this species should be accepted as type, regardless of 

 any other considerations. (Type by original designation. ) 



4a. RULE. If, in the original publication of a genus, typicus or typus is used as 

 a new specific name for one of the species, such use shall be construed as "type by 

 original designation. ' ' 



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 confusion later. 



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 subepecific 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 genus 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: 

 Agam odistomum . 



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. 



(b) Species which were species inquirendie 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 Linnsean genera select as type the most common or the 

 medicinal species. (Linnaean 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: 



