NO. 2 GENTRY : LAND PLANTS 95 



with the wide spread mesquite, Olneya tesota, Cercidium, and several 

 of the cactus trees. 



The known flora consists of only 77 species, which is considerably 

 less than one would expect on the basis of area and elevation of the 

 island. Obviously, Tiburon Island has been little collected and like other 

 islands in the California gulf, the summer-fall flora is unknown. When 

 the floras of Tiburon and adjacent Sierra Seri are better known, a com- 

 mon origin will probably become apparent that may show some degree 

 of independence from the surrounding region. Both Dawson and Rempel 

 visited Tiburon Island on the voyages of the Velero III. Their collec- 

 tions, consisting of 36 numbers were obtained on the southeast corner 

 of the island and add 1 1 plants to the recorded flora of Tiburon Island. 



Tiburon Island has the richest insular vertebrate fauna known in 

 the gulf. The following mammals are represented: coyote (Canis), rock 

 squirrel (Citellus), two species of pocket mice (Perognathiis) y kangaroo 

 rat (Dipodomys) , rock mouse (Peromyscus), wood rat (Neotoma), jack 

 rabbit (Lepus), and the burro deer (Odocoileus). Bird life is well rep- 

 resented and the following varieties appear to be endemic to the island : 

 Tiburon quail {Lophortyx gambeli pembertoni) , Tiburon woodpecker 

 (Centurus uropygialis tiburonensis) ^ Tiburon gnatcatcher (Polioptila 

 melanura curtata)^ Tiburon cardinal {Richmondena cardinalis town- 

 sendi)y Tiburon towhee (Pipilo fuscus jamesi). 



San Esteban Island lies in mid-channel \n the middle of the gulf 

 region o£E Tiburon Island. Quadrangular in shape, it embraces about 

 35 square kilometers of rugged land with a top elevation of 540 meters 

 at the south end. Volcanic in origin, it has ''scoriae-covered slopes and 

 much breccia" (Johnston 1924:954). It is shored mostly with high 

 vertical cliffs, but on the southeast is a pebble beach and a broad valley 

 above the beach provides ready ingress. No source of fresh water has 

 been reported. 



The ubiquitous Desert Shrub forms a fairly close cover over the 

 gentle valley gradients, where growth is fostered by run-off, and a widely 

 dispersed cover upon the open rocky slopes. The flora is very similar to 

 that of adjacent islands and there are no known endemics other than 

 the small number of plants it shares with neighboring islands, as Echino- 

 cereus grandis which is common to San Pedro Nolasco, San Lorenzo, 

 and San Esteban Islands. The mammal fauna consists of one endemic 

 species of Peromyscus and a colony of introduced rats, Rattus, 



The Velero III land plant collections from San Esteban Island, 

 Rempel 6 numbers, Dawson 6 numbers, consist mainly of cactus. The 



