1911.] Petrunkevitch, Index Catalogue of American Spiders. 7 



lowed the same rule as in Araneus, giving new names where it was necessary 

 and mentioning the provisional genus in parentheses. 



Departures from the Rules of Nomenclature. — It is unfortunate 

 that a great number of species have been described under names already 

 preoccupied by other authors. According to the rules of nomenclature 

 gradually worked out by the successive international zo5logical congresses, 

 such names should be regarded as homonyms and new names substituted 

 for them. This rule seems simple at the first glance, but many difficulties 

 appear when one begins to inquire into what really constitutes a homonym. 

 We have seen that the older authors had an entirely different conception 

 of genera from our own. It is evident that two identical names sounding 

 like true homonyms, one given, say by Walckenaer and the other by some 

 modern arachnologist, may not be really homonyms at all, since Walckenaer 

 included under his genera forms now assigned to entirely different ones. 

 Where an old species inadequately described, has not l)een placed by any 

 of the more recent arachnologists and another spider was in the mean time 

 properly described under the same name, it seemed to me to be wiser not 

 to change the later name since in the end it may be founfl not to constitute 

 a homonym of the earlier one. Similar pseudo-homonyms are met with 

 in almost all families of spiders. Another type of pseudo-homonym occurs 

 when one of the species has been described under a wrong genus. In this 

 case, it would, in my opinion, be equally objectionable to change the later 

 name. A few examples will illustrate this case. 



C Koch described a spider in 1846 under the name of Gasteracantha 

 jxiUida, and in 1849 Nicolet described an entirely dift'erent spider under 

 the same name. According to the rules of nomenclature the name of the 

 latter is a homonym and should be changed; but Gasteracantha pallida 

 (\ Koch is a synonym of Gasteracantha tctracantha hinmeus, while Gastera- 

 cantha pallida Nicolet belongs to the genus Glyptogona (Glyptogona pallida 

 Nicolet). Epeira cylindrica Taczanowski (1873) has priority over Epeira 

 cylindrica F. Cambridge, l)ut the former is a synonym of Epeira truncata 

 Keyserling. Why should then the Epeira cylindrica F. Cambridge be 

 given a new name? 



Under a true homonym I understand only identical names of such 

 species as actually belong to the same genus and there the older name 

 clearly has priority, as for example Tetragnatha hanksi McCook and Tetra- 

 gnatha banksi F. Cambridge. 



Another difficulty lies in the fact that some authors recognized two or 

 more genera which Simon later contracted into a single genus. Thus 

 Chrysso and Theridion are in Simon's system synonyms. Now Keyserling 

 described in 1884 a Chrysso nigriceps and in 1891 a Theridion nigriceps. 



