

NO. 2 FRASER : SCIENTIFIC WORK, VELERO III, EASTERN PACIFIC 139 



Southeast of Topolobampo Harbor the coast is of the same type found 

 throughout the whole State of Sinaloa, so that no collecting has been done 

 for another 175 miles, where there is one dredging station in 6-8 fathoms 

 off Point Piaxtla, which, for a change, forms a rocky headland. Even at 

 Mazatlan, 35 miles farther south, no marine collecting has been done. 

 The Velero III called here in December, 1931, but the collecting at this 

 time was all inland collecting. 



Although Mazatlan is the largest city on the coast between San Diego 

 and Panama, only the outer harbor is accessible to large vessels. The en- 

 trance is between Creston and Chivos islands. 



As Mazatlan is nearly directly east of Cape San Lucas, it may be 

 considered to be the southeastern limit of the Gulf of California; but, 

 commonly, Cape Corrientes, 175 miles farther south, is considered to be 

 the limit. 



For the first 70 miles from Mazatlan the trend of the coast line con- 

 tinues to the southeast and then turns more nearly southward. For about 

 100 miles from Mazatlan the coast is similar to that farther north, after 

 which it becomes more bold and rugged and the sandy islands and the 

 lagoons disappear. 



Lying 17 miles offshore, 50 miles south of the boundary between 

 Sinaloa and Jalisco and 90 miles north of Cape Corrientes, is Isabel 

 Island, 1% miles long, y 2 m ^ e wide, and 280 feet high, with several rocks 

 or rocky islets offshore. The main island consists of three large crater 

 cones, the half toward the water, in each case, having entirely dis- 

 appeared. Two of them, in vertical section, have the appearance of lava 

 formation, but the one facing south looks definitely like sandstone. Vege- 

 tation is sparse, but there is enough to show up distinctly on the north- 

 eastern slope, where it covers the surface quite fully. It is evidently a fa- 

 vorite resort and nesting place for myriads of frigate birds, terns, boobies, 

 and tropic birds. Two of the outlying rocks, close to the northeast point 

 of the island, are conspicuous. One of them is supposed to resemble a 

 swan. The only sand beach is a small one near the southeastern end of 

 the island. 



This island has been visited on five occasions for specimens, on land, 

 on sandy and rocky shore, on reefs, dipping near the surface, and on sand, 

 coralline, and nullipore bottom in shallow water, 25 fathoms or less. 



Approximately 40 miles to the southwest of Isabel Island are Las 

 Tres Marias Islands. The northernmost island, San Juanito, is a small 

 island, 2% by 1% miles, and the three main islands, Maria Madre, Mag- 



