978 REPORT OF NATIONAL MUSEUM, 1895. 



with their cliaracteristic bad-land topography, extend northward to 

 the Rosario Raviue. 



"The hamlet of Rosario is situated a few miles from the sea, in this 

 ravine or canyon, which extends inland for some 10 or 15 miles with 

 very gradual rise of its beds, and carries a small stream of running 

 water that in dry seasons sinks below the surface sands. [Plate 2.] 



"The cliffs of the canyon walls are eroded into castellated forms that 

 recall the buttes at Green River, Wyoming, familiar to travelers on 

 the Union Pacific Railroad. Opposite Rosario the bedding planes have 

 a dip of 15 degrees to the northeastward, while the surface of the mesa 

 is quite horizontal, and from the pebbles and recent shells on its sur- 

 face evidently represents a higher level of the ocean waters, which have 

 base-leveled it at about 1,000 feet above present sea level. For a few 

 miles north of the mouth of the Rosario Canyon the bluffs come close 

 to the present coast line and then gradually retreat, until opposite San 

 Quentiu they are about 8 miles inland. The immediate shore is first a 

 terrace about 200 feet above the sea level, then at the mouth of the 

 Socorro Valley a triangular-shaped Quaternary delta hardly 50 feet 

 above sea level, covered with rolled pebbles and recent marine shells. 

 The older beds forming the mesa region in this latitude, though not 

 markedly different from those between Bluff' and Canoas points, contain 

 a larger proportion of conglomerate material and several fossiliferous 

 beds of recent looking shells, among which were recognized Mytilus 

 californianus and a fragment of Pecten, like P. cerrosensis, which Dr. 

 W. H. Dall regards as indicating a probable Miocene age. These are 

 the beds seen by Gabb on his trip and called by him "mesa sandstones." 

 No evidence of unconformity between these and the Tejon beds was 

 observed, and it seems probable that they may constitute the highest 

 part of the mesa at Bluff' Point, but this was not determined by fossil 

 evidence. 



"Northward from Socorro River the bluffs of the mesa formation 

 retreat gradually from the ocean, and at San Quentin are separated 

 from it bythe sandy plains of Santa Maria, about 8 miles wide and 

 but a few feet above sea level, which are the northern continuation of 

 the depressions of the bay of San Quentin. The immediate coast line 

 at San Quentin is formed by a group of six conical hills of basalt, from 

 400 to 800 feet higTi, which, judging from the uneroded character of the 

 lava flows which have issued from their flanks, must be of very recent 

 eruption. One of these flows extending southward about 7 miles forms 

 the low, narrow tongue of land known as Cape San Quentin. It is evi- 

 dently the superior resistance of these hard lavas that has thus far 

 protected the plains of Santa Maria from the encroachments of the sea. 



WESTERN RANGE. 



" In the present topography the western range is very ill defined, and 

 consists of a number of irregular ridges and isolated mountain masses 

 15 to 20 miles from the coast, the highest summits of which are probably 



