32 BUREAU OF ANIMAL INDUSTRY. 



The following cases of this kind occur among nematode genera: 



NEMATODE GENERA WITH TYPE DETERMINED BY USE OF SPECIFIC NAME typlCUS. 



Allodapa Diesing, 1861 (typica=allodapa) ; also monotypical; also type by absolute 



tautonymy. 



Conocephalus Diesing, 1861 (typicus); also monotypical. 

 Dipeltis Cobb, 1891 (typicus); also type by original intention of the author (personal 



letter). 

 Tylolaimophorus de Man, 1880; also monotypical. 



Incidentally it may be noticed that Allodapa, Conocephalus, and 

 Tylolaimophorus are monotypical, 1 hence no other species could be 

 taken as types of these genera; further, typicaallodapa would be type 

 by absolute tautonymy. 

 Dipeltis represents an interesting case; it contained 



minor, new species, which would be type if "page precedence" were adopted 



blindly; 

 cirrhatus which is type of Dlscophora, 1875 (monotypical, and homonym 



[1836]); and 



typicus construed as type by original designation. In this case, accordingly, 

 the last not the first species is type. 



There is a further justification (if such were considered necessary) 

 for selecting typicus as type of Dipeltis. Suppose cirrhatus were 

 taken as type by inclusion; we should then have a species of Dipeltis 

 (which should be used instead of Discophora, 1875, preoccupied in 

 1836) with the name typicus yet not type of the genus, and this might 

 lead to later confusion. The same would apply if minor were selected 

 on the basis of page precedence. 



It can not be said that this method of indicating a tj r pe (by naming 

 a species typicus) is free from criticism, since it is likely to give rise 

 to confusion in future changes of classification. Thus, Conocephalus 

 typicus, 1861, has been placed in the genus Ascaris and is now Ascaris 

 typica, yet it is not the type of the genus Ascaris, 1758. 



Although, according to the Law of Priority, the name typicus must 

 hold (other things being equal) for the many species for which it has 

 been proposed, it will be well to avoid its use for. new species in the 

 future. Hence the 



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. 



For the specific n&mescommunis, medicinalis, officinalis, andvulgaris, 

 see p. 64. 



5. TYPE BY ABSOLUTE TAUTONYMY. 



RULE. If a genus, without designated type, contains among its original 

 species one possessing the generic name as its specific or snbspeciflc name, 

 either as valid name or synonym, that species or subspecies becomes ipso 

 facto type of the genus. 



Thus, let the genus X-us, 1890, without designated type, contain the 

 species alines, niger, and x-us. The species x-us becomes type of X-us 

 by absolute tautonymy. 



