DETERMINATION OF GENERIC TYPES, ETC. 9 



(a) 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. 



(6) 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. 



(c) All other things being equal, page precedence should obtain in selecting a 

 type. 



(d) Species based upon sexually mature specimens should take precedence over 

 species based upon larval or immature forms. 



(e) All other things being equal, show preference to a species which the author of 

 a genus actually studied at or before the time he proposed the genus. 



(/) Show preference to a species bearing the name communis, vulgaria, medidnalis, 

 or officinalis. 



(g) Show preference to the best described, best figured, best known, most easily 

 obtainable species, or of which a type specimen can be obtained. 



(7i) Show preference to a species which belongs to a group containing as large a 

 number of the species as possible. 



(i) In parasitic genera, select if possible a species which occurs in man or in some 

 food animal, or in some very common and widespread host. 



By following the foregoing rules and recommendations, types may be designated 

 for the great majority of genera without reference to any subjective interpretation of 

 diagnosis or anatomical characters and their value; in the majority of cases the type 

 will be selected largely on the basis of the original publication, yet the inconveni- 

 ences connected with the " rule of page precedence" will be very largely avoided. 



In connection with correlated nomenclatural questions, the conclusion is drawn 

 that the principle of "synonymy by original publication," despite its Draconian 

 nature, is a just rule to follow (p. 68). 



The "rule of homonyms" for absolute homonyms, as provided for in the Interna- 

 tional Code, is unreservedly adopted (p. 69), but the Merton "rule of phononyms" 

 (p. 72) is rejected, while doubtful homonyms (p. 73) are accepted as distinct 

 names. 



It is a matter of regret that we do not see our way clear to apply the rule for emen- 

 dation until its supporters accomplish the vast amount of pioneer work (p. 76) 

 which is prerequisite to a practical application of their rule;- hence, for the present, 

 we find ourselves forced to continue to use "original orthography," be this good, 

 bad, or indifferent. 



Contrary to some authors it is maintained (p. 78) that misprints have a definite 

 nomenclatural status. 



The Law of Priority is not a new idea, as assumed by some zoologists, but dates 

 from Linnaeus, and contrary to the apparent assumption of some writers, it was 

 accepted by Rudolphi in 1801, who proposed a code of nomenclature (p. 78) 

 which has been very generally overlooked. 



Some of the difficulties of which some authors complain in helminthological 

 nomenclature could be obviated if the rule relative to polynomial authors (p. 80) 

 were to be more rigidly enforced for authors between 1758 and 1819. By an agree- 

 ment among helminthologists, to the effect that certain doubtfully binomial works 

 were to be considered polynomial, and therefore excluded from consideration in 

 nomenclatural matters, not an inconsiderable number of the difficulties which arise 

 could be avoided. 



Part II contains a list of all-the roundworm genera accessible in the card catalogue 

 of the Bureau of Animal Industry, together with certain other genera which are cited 

 for practical reasons. With each genus the original species are given, and in most 

 instances the type species is definitely fixed. 



Bibliographic references in this paper are taken from the Index-Catalogue of Med- 

 ical and Veterinary Zoology (Bulletin No. 39, Bureau of Animal Industry). 



