62 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



24. Woodring (1925, p. 72) and Cox (1948, p. 64) revived the cor- 

 rect spelling and dated Pseudamussiuin (as a subgenus) from the 

 Adams,' with Pecten hybridus Gmelin as type. 



25. Stewart (1930, p. 122) dated Pscudamussium from Morch and 

 said, ". . . Pecten septemradiatus Miiller, is the type by absolute 

 tautonymy since Morch placed "P. pseudamussium Ch." in its 

 synonj'my; . . ." In this instance "absolute tautonymy" is incorrect, 

 for Morch placed Chemnitz' species in the synonymy of Miiller's 

 only because he accepted Chemnitz' erroneous description and 

 figures. 



26. Grant and Gale (1931, p. 235) dated Pseudamussium (as a sub- 

 genus) from "Klein in Morch," with Pecten hybridus Gmelin as 

 type. 



27. Thiele (1934, p. 807) and Rowland (1938a, p. 61) followed 

 Stewart. 



28. North (1951, p. 231) presented a thorough analysis of the prob- 

 lems, concluding that the genus dates from the Adams', the type 

 species is Ostrea hybrida Gmelin, and Dall first validly designated 

 the latter as type in 1898. 



Summary: The central facts are these: the confusion as to the valid 

 name for the west African shell was the result of Chemnitz' errors ; the 

 confusion as to the valid type species resulted from Morch's acceptance 

 of those errors and the addition of his own. Thus, apart from the status 

 of Morch's catalogue, on which the validity or invalidity of his proposal 

 of the genus rests, Chemnitz' errors are seen to be the root of the matter. 

 As a further result of those errors, if the International Commission on 

 Zoological Nomenclature were to suspend the rules (as is permissible 

 under the 1913 Monaco resolution) and accept the names in Morch's 

 catalogue, we could still not accept as type either of the two species he 

 cited, and Dall's 1898 designation of Pecten hybridus Gmelin would re- 

 main the first valid designation. A brief recapitulation of the three prob- 

 lems follows: 



A. The genus Pseudamussium must date from the Adams brothers. 

 It cannot date from Klein, who was pre-Linnean, or from Herrmannsen, 

 who gave no diagnosis or indication. Nor can it date from Morch, whose 

 sales catalogue was not a valid publication, according to the definition of 

 that term as clarified by the International Commission on Zoological 

 Nomenclature in 1948. 



B. The valid name for the west African species is Ostrea hybrida 

 Gmelin. Both Lister and Klein are invalid. Chemnitz, whose specific 



