51 



together in the same geographic region. Most of them range along the 

 coast from the head of the Gulf to Panama, but a few are restricted to the 

 southern Gulf, or are not found north of Mazatlan. 



There are many other species of invertebrates known from other col- 

 lections, which are more abundant on the sand beaches and on sand bottom 

 to depths of 10 meters, and are perhaps more typical of this environment 

 than those given in Table II. McLean (1961) lists two sand dollars, 

 Encope grandis L. Agassiz and Encope californica Verrill, as living on the 

 sand flats at Los Angeles Bay, and although Encope tests were frequently 

 noticed on the beaches, no living specimens were collected along the beach 

 during this present study. Dushane (1962) also gave a large list of mullusks 

 found on sand or sand-mud bottom at the same depths near Puertocitos. 

 She included at least 112 moUusk species which definitely live in this 

 environment. The mollusks found alive on the sand flats to depths of 

 four or five meters in Los Angeles Bay by McLean are given in a list below 

 in order to illustrate the diversity of species from one locality in one 

 environment. 



Prosobranchs 

 Calliostoma eximum 

 Neritina luteofasciata^ 

 Balcis cf. rutila 

 Cerithium sculptum 

 Cerithium albonodosa^ 

 Cerithidea mazatlanica 

 Natica chemnitzi 

 Polinices bifasciatus 

 Polinices uber 

 Polinices reclusianus 

 Strombus gracilior^ 

 Strombus granulatus^ 

 Hexaplex erythrostomus 

 Nassarius iodes 

 Nassarius moestus 

 Nassarius tiarula^ 

 Oliva spicata^ 

 Olivella dama 

 Cancellaria cassidiformis 

 Conus ximines 

 Terebra variegata 



Tectibranchs 

 Bulla gouldiana^ 



Haminoea angelensis 

 Haminoea strongi 



Pulmonates 

 Melampus olivaceous 



Lamellibranchs 

 Anadara multicostata 

 Anadara cepoides 

 Glycymeris gigantea 

 Glycymeris maculata 

 Glycymeris multicostata 

 Pinna rugosa 

 Atrina tuberculosa 

 Trachycardium consors 

 Trachycardium panamense 

 Trigoniocardia granulifera 

 Laevicardium elenense 

 Laevicardium elenense apicinum 

 Pilar newcombianus 

 Megapitaria squalida^ 

 Dosinia ponderosa 

 Protothaca grata 

 Heterodonax bimaculatus^ 

 Lyonsia gouldii 



^) Species also taken alive in the sand beach and sand flat environment in the present 

 study. 

 4* 



