Pacific Tunicata 



of the 



United States National Museum 



Introduction 



The previously unidentified Tunicata in the U.S. National Museum 

 listed and described herein were collected from various parts of the 

 Pacific, with the exception of the west coasts of North, Central, and 

 South America. Most of the specimens belong to Ascidiacea, but a 

 small number are pelagic tmiicates, including Appendicularia, Thalia- 

 cea, and Pyrosomata. 



x\s studies of the ascidian fauna in various parts of the Pacific 

 are in progress I think it better, at present, to refrain from writing 

 on general aspects of the ascidian fauna of the Pacific, leaving them 

 for a future paper. 



Many simple ascidians are identified rather easily, while the identi- 

 fication of compound ascidians is usually very exacting. Even repeat- 

 edly described species might be confused with others, as the range 

 of intraspecific variation is not yet clearly defined for most species. 

 Under these circumstances, it is rather useless to list only the species 

 found in the material. Inevitably accurate descriptions accompanied 

 Avith exact figures for those species must be made. Thus in this paper, 

 most of the compound ascidians are described in detail, while most 

 solitary forms are noted briefly. 



In descriptions of the branchial sac, the number of stigmata in 

 respective rows and of branchial plications is always given for only 

 one side of the sac. The number of inner longitudinal vessels on 

 respective branchial plications indicates the total number of vessels 

 on both surfaces of each plication. 



The specimens treated in this paper were examined during my stay 

 at the United States National ]\Iuseum, from February to April 1957, 

 work which was supported with the financial aid of the National 

 Academy of Sciences. I am very grateful to the staff of the United 

 States National Museum, ])articularly the members of the Division 

 of Marine Invertebrates, Dr. Fenner A. Chace and others, for grant- 

 ing me the space in the museum for research and assisting me in 

 obtaining financial aid. Dr. Frederick M. Bayer, at that time of the 



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