THE DETERMINATION OF GENERIC TYPES, 



LIST OF ROUNDWORM GENERA, WITH THEIR ORIGINAL AND 

 TYPE SPECIES. 



BY CH. WARDELL STILES, PH. D., 



Zoologist of U. S'. Public Health und Marine- Hospital Service; Consulting 

 Zoologist of Bureau of Animal Industry, 



AND 



ALBERT HASSALL, M. R. C. V. S., 

 Assistant in Zoology, Bureau of Animal Industry. 



SUMMARY. 



Part I contains a general discussion on determination of generic types. 



A genus without a type species is like a ship without anchor or rudder, and a 

 failure on the part of authors to designate types has heen one of the most fruitful 

 sources of trouble in systematic zoology and nomenclature. The existing codes of 

 nomenclature recognize the importance of type species, but the rules for their deter- 

 mination are not explicit enough, while the views on the method of determination 

 vary greatly among authors. 



It seems desirable, but at present impracticable, to have complete, objective rules 

 covering type determination, whereby the subjective element may be entirely elimi- 

 nated, and whereby all types may be determined purely from the literature, without 

 reference to the diagnosis or anatomy of an animal. Page precedence, as supported 

 by many systematists, would accomplish this, yet would lead to many difficulties; 

 still it must be admitted that this rule has great advantages despite its disadvantages. 



Although it seems impracticable at present to attempt to adopt any complete series 

 of rules on type determination which shall be followed seriatim, still satisfactory 

 rules can be formulated which will cover the majority of cases that arise, and these 

 rules may be supplemented by recommendations which bring to mind methods 

 which it will be well to follow, unless strongly contraindicated by practical consider- 

 ations. AVhile urging zoologists to designate the type of every new genus proposed 

 in the future, we shall suggest to the International Commission on Zoological Nomen- 

 clature the following rules and recommendations, as amendments to the Code, for 

 guidance in determining the types in the case of older genera. 



1. RULE. A genus proposed with a single original species takes that species as 

 type. (Monotypical genera. ) 



2. RULE. The type of a genus (containing, from the standpoint of the original 

 author, both valid and doubtful species) must never be selected from the species 

 which the original author of the genus clearly designated as species inquirendse at 

 the time of the publication of the generic name. 



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