104 



This is not surprising, as the Persian Gulf is noted for it's extremely high 

 temperatures and also hypersalinity. These extremes may be limiting to 

 a large number of invertebrate species. One community on shell gravel 

 was characterized by a species of Branchiostoma (thus parallelling Samuel's 

 community off Madras), a species of Venus, a Glycymeris and a polychaete, 

 Temnopleurus. A Branchiostoma community may exist in the Gulf of 

 California from preliminary observations, but was not sampled. The only 

 other community described by Thorson from the Persian Gulf in shallow 

 depths and on sand bottom was the Xenopthalmus pinnotheroides crab 

 community. The community was completely dominated by this small 

 crab, accompanied by a few polychaetes of no quantitative significance. 

 Apparently, there was nothing like the diversity of species found in the 

 Gulf of California in either the Persian Gulf or Bay of Bengal. 



Buchanan (1958, p. 21-23) describes an "inshore fine sand community" 

 from depths of six to 15 meters off Accra, Ghana on the West African 

 coast. In overall aspect, the fine sand community was characterized by 

 two animals, the pelecypod, Cultellus tenuis (related to Ensis), and the 

 polychaete worm, Diopatra neopolitana. Within the major structure of 

 this community, three smaller communities were found which he called: 

 (1) the Owenia beds, (2) the Accra Bay silt patch {Macoma bed), and (3) the 

 Dentalium zone. The distribution of these small communities within the 

 six to 15 meter depths off Accra is reproduced in fig. 28. This picture is 

 quite similar to that shown in fig. 16 for the pattern of distribution of the 

 computor-designated groups of species in similar depths in the Tiburon 

 region. Buchanan attributed much of the patchiness of these communities 

 to small differences in grain size, organic matter content, and possibly 

 wave action. However, he found that there was nothing to distinguish the 

 environment of the Owenia beds from the rest, unless larval settlement of 

 the dominants had been influenced by the direction of the prevailing 

 current. Similar invertebrate species are also found in the Tiburon near- 

 shore sand bottoms, such as Ensis, Tagelus, several species of Tellina and 

 Macoma, and many tube-forming polychaetes, not yet identified. There 

 are minute differences in sediment types in this area, even though sands 

 predominate throughout (fig. 8). The group "7" assemblage, using Laevi- 

 cardium elenense as the key species, seems to be confined more to the 

 silty-sand portion of this environment, while the Chlamys circularis group 

 is more closely allied with shell-sand and shell-gravel sediments at slightly 

 greater depths. Mollusks were the typical components of these groups, 

 with pelecypods outnumbering the gastropods. The other index groups 

 contained more gastropods or crustaceans. The minute differences of 

 environmental factors within the major environments have yet to be 



