26 CALIFORNIA ACADEMY OF SCIENCES. 



dipping soft shales and sandstones of cretaceous or ter- 

 tiary age (mesa sandstones). These are again, especially 

 near the Gulf, covered with recent eruptive masses. Met- 

 amorphic rocks do not make their appearance until fur- 

 ther north, and then, according to Prof. Gabb's views, 

 they are derived by regional or contact metamorphism — 

 from the mesa-sandstones. On the whole, the general 

 outline of the geology of the peninsula, given above, would 

 be the same from La Paz to Sta. Gertrudis, that is from 

 Lat. 24° to Lat. 28°. In general, we may characterize 

 the structure as that of a gently ascending table land, 

 broken near the eastern coast b}' a very considerable 

 fault. This fault line may be very old, but at any rate a 

 large dislocation occurred along it in post-cretaceous time. 



It would be very singular if the occurrence of older 

 schists were confined to a single point on the west coast 

 of the peninsula. 



However, consulting the excellent maps of the h3^dro- 

 graphic office it is seen at a glance that the Sta. Marga- 

 rita and Magdalena Islands, continued by the rocky mass 

 of Cape San Lazaro, form a broken chain striking about 

 N. 40° W., and extending for about 45 nautical miles 

 Mr. Brandegee, who was a member of the expedition 

 mentioned above, states that Magdalena Island has the 

 same geological structure as Sta. Margarita, and that 

 from its appearance Cape San Lazaro is also composed 

 of similar rocks. The highest point on Sta. Margarita 

 Island attains 1900', while that of the Cape is about 

 1300'. 



North of the cape the coast makes a bend eastward 

 (see fig.) forming a long, shallow bay until at a distance 

 of 130 nautical miles, and in a direction of about N. 

 30° W. Point Abreojos is reached. From here to Point 

 San Eugenio (no miles) the coast trends N. 45° W., 



