28 CALIFORNIA ACADEMY OF SCIENCES. 



amphibolite and serpentine, together with granite and 

 porphyries. Besides, basaltic flows and fossiliferous 

 sandstone are mentioned. 



In all probabilit}^ the range south of Cerros Island is 

 in composition and age similar to the northern end, and 

 the contrast between the more recent eastern range, form- 

 ing the main mass of the peninsula, and this western 

 older range of crystalline rocks is equally strong, as in 

 the section from Sta. Margarita Island eastward. If we 

 now examine the sea bottom between Point Abreojos and 

 Cape San Lazaro by means of the soundings recorded on 

 the hydrographic charts, it will be found that the 

 thousand-fathom line which at Point San Eugenio runs 

 within 15 miles of the shore, does not follow the coast 

 line, but runs in a southeasterly direction till it again ap- 

 proaches the shore near Cape San Lazaro. Along a 

 straight line between the two promontories the average 

 depth is, according to the few soundings available, not 

 more than 100 fathoms. 



All these data speak strongly in favor of a submarine 

 continuation of the Viscaino Range towards the Cape 

 San Lazaro Range. 



Going southward from Sta. Margarita the relations are 

 somewhat similar. For about 80 miles southeast of the 

 island, the low coast occupied by the mesa sandstones 

 forms a slightly curved line; it then trends southward, 

 and the Sierra de la Victoria, rising from the sea to a 

 height of over 6000', runs along it until at the rocky 

 headland of San Lucas the southern end of the peninsula 

 is reached. 



The thousand-fathom line between Sta. Margarita and 

 the northern end of Sierra de la Victoria forms a 

 curve, concave towards the shore, and distant more than 

 30 miles from it. Along a direct line between the island 



