»K(.EEj BARREN VALLEYS AND RANGES 41 



the intei'ior. At Punta Antigualla the bank expands and rises into a 

 great manimillated shell mound nearly 100 feet high, with several of 

 the cusps occupied by more or less ruinedjacales; and occasionally occu- 

 pied houses occur midway thence to the southernmost point of Sierra 

 Seri, and agaiu at the base of the first spur east of Punta Ygnacio. 

 Beyond Punta Antigualla the sweep of the waves is stronger than m 

 Bahia Kino, and the coastal sandbank is generally higher. Between the 

 rocky buttresses of Punta Yguacio and the next spur eastward the sand- 

 ridge rises fully 50 feet above mean low tide, and here, as elsewhere, 

 its verge is protected by a fog-fed chaparral thicket with occasional 

 clumps of okatilla and other cacti. Behind the coast barrier lie lagoon- 

 like basins, generally dry and floored with saline silt-beds, though 

 sometimes occupied by briny pools formed through seepage during 

 southwesterly gales; and there are i)hysiographic indications that the 

 northwestward extension of Laguna la Cruz formerly stretched some 

 miles farther than now and lay in the rear of Punta Antigualla in 

 such wise as to form a source of supply of the clam-shells of which the 

 eminence is built. 



2. Sierra Seri is a double range, divided mid-length by a broad saddle 

 barely 2,000 feet in height.' Like other Sonoran ranges, the nucleal 

 jiortions are exceedingly rugged and precipitous — at least two of its 

 picachos shoot so boldly that they commonly seem to overhang, and 

 have been called leaning peaks. In large part the precipices rise 

 abruptly irom a symmetrical dome molded by sheetflooding, much as 

 the insulated buttes rise from the Bacuache fan in northeastern Seri- 

 land; so that the tract lying between Desierto Encinas and El Infier- 

 nillo is a composite of exceptionally precipitous and exceptionally 

 smooth mountain slopes. One of the Seri trails radiating from Bar- 

 ranca Salina lies across the mid-sierra saddle; others push into several 

 mountain valleys, and the largest leads to Tiuaja Trinchera, at the 

 base of Johnson peak, where there are a few low walls of loose-laid 

 rubble, somewhat like those of the trincheras (entrenched mountains) 

 farther eastward — the only structures of the sort seen in Seriland. 

 Toward the southern end of the range lie various trails, the most con- 

 spicuous paralleling the coast, either near the shore or over the steep 

 salients, according to the configuration ; while here and there ruinous 

 jacales a few yards from the coast attest sporadic habitation. The 

 eastern shore of Bahia Kunkaak from Punta Ygnacio northward 

 reveals a typical geologic section of the Sonoran province: the trans- 

 gressing waves have carved in the granitic subterrane a broad shelf 

 lying just below mean low tide and usually stretching several furlongs 

 oft'sbore; this shelf is relieved here and there by remnantal crags of 

 obdurate rocks, cumbered by bowlders and locally sheeted with sand 

 and arkose derived from mechanically disintegrated granite; while the 



' The nortlierii portion, as seen from the east, is shown in plate III; the southern portion, as seen 

 from the west, appears in Iht* upper part of plate IV. while the southwesternraost point is shown in 

 the lower part of the same plate. 



