SPONGES OF THE GULF OF CALIFORNIA 



(Plates 1-97) 

 Malcolm Gibson Dickinson 



INTRODUCTION 



The Gulf of California is a geographical unit. Its boundaries are 

 definitely established by land on three sides. It is also, in a sense, a time 

 unit, since its beginnings in the Eocene, extension in the Miocene, and 

 continued existence to the present give it a definite age. 



These durational boundaries make the region unique among the marine 

 areas of a like size. Most coastal regions of the present oceans, such, for 

 example, as the coast of California or even the Gulf of Mexico, have 

 existed throughout known time, undergoing many changes of shape and 

 shore but still continuing to exist. 



These unusual features give the fauna of the Gulf of California a 

 peculiar interest. It came into being in the Eocene and Miocene periods 

 w^hen, for at least part of the time, a water connection existed between 

 the Atlantic and Pacific Oceans across Mexico. No known earlier fauna 

 existed in the region, and it is there that a migratory fauna might be 

 expected to establish itself. For this reason a study of the fauna of the 

 Gulf region should logically be expected to furnish evidence on the 

 ancestry and relationships of many of the Pacific coast forms. 



With the exception of the work done on the cruise of the Albatross in 

 1891, the sponges of the Gulf of California have not been collected for 

 a detailed scientific study. The records indicate that on the Albatross 

 cruise three species of sponges were collected from the Gulf of California. 

 All of these were deep-water forms, since the Albatross collecting was 

 done largely at considerable depth. Such sponges are not of great signifi- 

 cance as representative forms of a region, since the deep-water sponges 

 are almost invariably cosmopolitan. 



This lack of data on the sponge fauna to the south of California, 

 including the Gulf region, has made it difficult to properly relate the 

 sponges of California to those of other geographic areas. The California 

 sponges have long been considered to be an isolated group, their origin a 

 puzzle, and their relatives unknown. 



With this background, the author began in 1935 his study of the 

 sponges of the Allan Hancock Foundation collections. The results of 



[1] 



