50 



described by Parker (1956 and 1960). In extent, this environment and its 

 assemblage covers almost as much shoreline as the rocky shores, as shown 

 in fig. 14. One third to one half of all known mollusk species from the Gulf 

 of California have been reported from this environment, since the majority 

 of records are a result of collecting along sand beaches which are most 

 accessible from human habitation. It is difficult to ascertain from the 

 literature which species were found in the living state in this environment 

 alone. Thus the characteristic species, which are listed in Table II are 

 those from the present collection, with the exception of a special list 

 extracted from McLean (1961) given below. 



As on the rocky shores, collecting along the sandy shores was also 

 somewhat haphazard, and most of the samples along the shore were taken 

 by hand. The subtidal portion of the environment, however, was sampled 

 mostly by grab samples (Table III, fig. 2a), i.e.: 3 orange peels, 5 Van 

 Veens, 1 dredge, 2 minidredges and 2 by diving. Because most of the hard- 

 shelled animals which may live to depths of 10 meters may also wash 

 onto the shore and become incorporated into sand beach deposits, no 

 distinction was drawn between the tidal and subtidal portions of this 

 environment. There is certainly a different group of animals living in the 

 deeper portions of this environment than right at the shoreline. 



Only three species were assigned to a group of stations in this environ- 

 ment by the computor program, Cardita megastropha, Tivela byronensis 

 and Heterodonax bimaculatus, of which only Heterodonax can be considered 

 a characteristic species, the other two not even having been taken alive. 

 In a number of localities it was observed by the author that Heterodonax 

 could be scooped up by the handfuls by digging just below the sand surface 

 at the water's edge. The other two species, although not taken alive during 

 this study, are listed as typical nearshore sand bottom species by other 

 authors. The typical animals found at the water's edge, as observed by this 

 author are: Cerithium albonodosum, Bulla gouldiana, Heterodonax, nume- 

 rous species of Donax, Uca crenulata and Ocypode occidentalis. The other 

 species given in Table II are typical of the sub-tidal portions of this 

 environment. In the sub-tidal portions the most abundant living species 

 and also the most characteristic are : the gastropods, Strombus gracilior, 

 Oliva spicata, Olivella anazora; the pelecypods, Transanella puella, Mega- 

 pitaria squalida, and the most important Tellina felix; and the echinoid 

 Eucidaris thouarsi. The list of abundant, although not taken alive, species 

 on Table II for this environment is also given, since it is known that most 

 of these species have been recorded as living in this environment by others, 

 and can be considered useful index species for the paleontologist. Although 

 all species given in Table II occur in this environment, not all occur 



