27 



(CuRRAY, in VAN Andel, d a/., in press). There are many small pocket 

 beaches on both sides of the Gulf, which do provide a niche for sandy- 

 beach fauna, but sandy beaches are not as extensive as they are along the 

 coast of the Gulf of Mexico. 



Estuarine coastal lagoons are rare in the Gulf of California proper, 

 which receives virtually no rainfall, but very large lagoons are to be found 

 south of Mazatlan, where the climate becomes humid. Information con- 

 cerning these lagoons was obtained from Fred B Phleger and Joseph 

 R. CuRRAY (oral communication), and from the literature, particularly 

 Keen (1958). There are a number of semi-enclosed bays on the west side 

 of the Gulf, where normal Gulf conditions occur, and a few strictly tidal 

 to hypersaline lagoons on the east side from Guaymas to the north. There 

 are also some very large lagoons near the vicinity of Los Mochis (fig. 1). 

 Little is known concerning their fauna. The configuration of the shoreline 

 of the Gulf of California is so variable that a tremendous number of 

 ecological niches are present for marine and intertidal invertebrates. 



The continental shelf region was sampled in considerable detail, although 

 in only two main regions, namely, off the Costa de Hermosillo and Costa 

 de Nayarit. Here the shelves are relatively broad and gently sloping, 

 providing niches for many assemblages which parallel those found on the 

 broad shelves of the Gulf of Mexico. On the other hand, the rocky and 

 sandy continental shelf on the west side of the Gulf of California from 

 Angel de la Guarda Island to Cabo San Lucas (fig. 6) is very narrow, and 

 in some places virtually non-existent. The west side of the Gulf is therefore 

 inhabited primarily by epifaunal species of invertebrates, since little 

 soft level-bottom area is available for infaunal species. Alternatively, the 

 upper Gulf, north of Tiburon and Angel de la Guarda Islands, is very 

 similar to the Gulf of Mexico shelf. One fairly deep, broad basin (Tiburon 

 Basin) exists between the islands, but in general there is a broad, gentle 

 shelf descending from the Colorado delta to depths of about 200 meters 



(fig. 6). 



In contrast to the strictly northern portion of the Gulf, the southern 

 and central portions are characterized by deep channels and basins, with 

 steep rocky sides descending to over 2,000 meters. The bottom of the basins 

 themselves are flat, but the total area suitable for level-bottom communi- 

 ties is rather small compared to the total area of the Gulf. The bathymetry 

 of the Gulf of California was first drawn up in detail by Shepard (1950), 

 based principally upon soundings obtained on the "E. W. Scripps 

 Cruise" in 1940. Byrne and Emery (1960) gave a simplified version of 

 this chart, but added no new information. A new chart of the bathymetry 



