GENERAL DISCUSSION 



Introduction 



The quarter century following the appearance in 1925 of the Rathbun 

 monograph, "The Spider Crabs of America", has been a period of 

 intensive exploration in the eastern Pacific, unrivaled since the pioneer 

 investigations of the United States Exploring Expedition, the Hassler, 

 and the Albatross, and in some respects exceeding them in productivity. 

 Numerous well-organized and splendidly equipped expeditions have 

 converged upon the Gulf of California, the Bay of Panama, and the 

 Galapagos Islands, accompanied by carcinologists of a younger genera- 

 tion whose experience in the field has found expression in a growing 

 body of literature in which distributional, ecological, and behavioristic 

 factors are emphasized. The establishment of the Allan Hancock Foun- 

 dation as a permanent repository for the marine invertebrates obtained 

 by the Velero HI and Velero IV has served to attract to the west coast 

 other major collections gathered during this most fertile period. 



The publication by Balss (1929) of a suggested revision of the Oxy- 

 rhyncha invited changes in the classification adopted by Rathbun, which 

 was essentially that of Alcock (1895). The use of the male first pleopod 

 as a taxonomic character, revived by Stephensen (1945) after a period 

 of neglect since Brocchi (1875), provided a fertile field for investiga- 

 tion. It is not surprising, therefore, that the application to this large 

 mass of specimen material of a new analysis and an improved technique 

 should result in a clarification of the interrelationships of the genera and 

 species of Pacific American Majidae and the placing of their systematics 

 on a firmer basis than has been possible heretofore. 



If a single example may be chosen to illustrate the great strides that 

 have been made in our knowledge of the occurrence of majid species in 

 the eastern tropical Pacific, let it be the genus Podochela, of which Rath- 

 bun (1925) was unable to list a member south of Cape San Lucas, with 

 the exception of P. jnargaritaria of the Galapagos Islands. With the 

 addition of new species described by Finnegan (1931), Garth (1939, 

 1940, and the present volume), and the extension of range of species 

 previously reported from the Lower California-Gulf of California region, 

 the number of species of Podochela known to inhabit eastern Pacific 

 waters has been increased to 10, a number equaling the representation 

 of the genus in the western Atlantic. To cite a similar example from 

 among the Parthenopidae, the genus Parthenope Weber was represented 

 from the eastern Pacific in the collections of the U. S. National Museum 

 as recently as 1925 by an even dozen specimens, of which nine were of 



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