13 



The older records are frequently obscure and often of doubt- 

 ful validity, which leads in many cases to divergent opinions 

 among experts as to the proper application of the laws of pri- 

 ority governing in such cases. To the layman who lacks access 

 to the original documents, these nomenclatorial disputations 

 appear at times like the wrangling of lawyers over the techni- 

 calities of the civil law. No decision appears to be final. 



As has been indicated Dall ascribed the founding of the 

 genus Thais to Bolten, but Clench (1947) is inclined to the view 

 that this honor belongs rather to Roding. 



A similar divergence of opinion has appeared in connection 

 with the question as to the subgeneric status of the forms of 

 Thais inhabiting the North Atlantic and North Pacific areas. 

 Dall (1915) in his revision of our west coast species placed all 

 of these forms in the subgenus Nucella. Clench however on 

 what would seem to be indisputable grounds, argues that the 

 subgenus Polytropa Swainson takes precedence over Nucella 

 Roding. 



Dr. Clench in his survey of the forms of Thais representing 

 the southern division of this genus, gives us a clear-cut analy- 

 sis of this difficult group, the members of which, like many 

 other forms exhibiting polymorphic tendencies, have received 

 an over-supply of names, with much resulting synonomy. 



As Dr. Clench has pointed out, the southern group of Thais 

 differ from their northern relatives in their manner of repro- 

 duction, the young being hatched from a fixed egg-mass as 

 a free swimming veliger larval form, which greatly increases 

 their powers of distribution, and thus tends to form less dis- 

 tinctive local races except in a broadly geographic sense, as 

 in the case of the subspecies of Thais rustica found upon 

 the isolated island of St. Helena. 



Clench has suggested it might be desirable to separate 

 generic dly the two groups of Thais forms. 



Although the writer has no material of the southern Thais 

 for comparison, it seem probable that more detailed popula- 

 tion studies should prove interesting. 



