40 



WEST SIDE, GULF 



EAST SIDE, GULF 



ApproN 23" N. tol. 

 CABO SAN LUCAS- 

 (205-29'C 



DEEP CENTRAL 



GULF *!""■""•'"-... pes^jco 



(I«9-3I2*C1 



Fig. 12. Zoogeographic breaks in faunal distribution in the Gulf of California, based on living 

 ranges of common invertebrate species, as revealed from distributional data from this study 

 only. Thickness of the bars is related to the number of species within each zoogeographic break. 

 The two small sets of graphs demonstrate the total number of species with northern and 

 southern limits at each temperature break on both sides of the Gulf. 



There is a partial break in distributions at Los Mochis, where a major 

 headland exists, although the presence of a temperature barrier at this 

 point is not known. It is known, however, that the Los Mochis region 

 represents a transition from arid to sub-humid climate, as well as a change 



