47 



Description of the Macro-Invertebrate Assemblages and 

 Environments 



The present sample coverage and available data is inadequate for a 

 thorough discussion of all of the possible assemblages that might exist 

 in the Gulf of California, but it is at least possible to describe the more 

 important ones and especially those that are likely to occur in the fossil 

 record. The number of ecological niches, both large and small, is very 

 great for such a relatively small region, particularly along the rocky, 

 dissected coast of the west side of the Gulf. The fine-grain carbonate mud 

 environments are the only ones completely missing from this region. There 

 are small patches of coral reefs (Squires, 1959), but they do not compare 

 in size with those of the Caribbean and Indo-Pacific regions. On the other 

 hand, with the exception of the fine-grain carbonate environments, almost 

 all other possible environments of deposition which have occurred during 

 the Tertiary history of the Americas can be found in the Gulf of California. 

 The polychaetes some of the Ophiuroids and Asteroids, Anthozoans, 

 Sponges and Bryozoans have not yet been identified; therefore, these 

 assemblage lists are incomplete, especially with regard to the smaller and 

 sometimes most abundant animals, which have served to characterize 

 communities in other regions. 



I. The intertidal and shallow rocky shores assemblage. 



The fauna of the intertidal rocky shore environment inhabits the major 

 portion of the shoreline of the Gulf of California and along the coast of 

 Middle America. It is also possibly the most easy to recognize, either 

 in situ or in older sediments. Many papers have been written on the 

 composition of the rocky intertidal fauna and flora of the world, partic- 

 ularly the series of papers by the Stephensons, too numerous to cite here, 

 and a review by Doty (1957). The majority of these papers have been 

 concerned with the intertidal zonation in temperate or boreal regions, 

 where attached algae play an important role in influencing the composition 

 of the fauna. Very few papers give a comprehensive idea of the composition 

 of the intertidal rocky shore fauna of the fantastically rich Gulf of Cali- 

 fornia region. Some idea of the diversity of mollusks to be found in this 

 habitat can be obtained in Steinbeck and Ricketts (1941), Keen (1958), 

 McLean (1961) and Dushane (1962). It would be impossible to list here 

 all of the animals known to occur in this environment, but at least the 

 most common ones found in this study and a few others known to be 

 abundant from other papers are given in Table II of the appendix. 



