52 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Gold. — The only mineral of economic consequence that has 

 been found in this district is gold. The stream gravels oc- 

 curring along the canyons, especially on the Navajoa creek 

 near the granite area, and along the small canyon one mile 

 west of La Panza Post Office have been found to be gold bear- 

 ing. During the period from 1880 to 1886 considerable inter- 

 est was felt in these localities on account of the discovery of 

 gold, and some placer mining was done along the stream beds 

 but no large mines were developed. As a matter of history 

 this district was known to contain gold before it was discovered 

 by Marshall in 1848 at Coloma. 



It is stated that over $1,000,000.00 in gold has been taken 

 from these placers.^ The De La Guerra gulch was the principal 

 source of the gold. 



Other Metals. — There are deposits and veins of other metals, 

 as hematite and chromic iron, known in certain parts of the 

 district, though they are perhaps not important. 



On Section 25, Township 30 South, Range 17 East, there 

 is an outcrop of iron gossan that can be followed for a distance 

 of 1000 feet or more along the east side of the San Juan River. 

 It appears to have a thickness of five to eight feet and to cut 

 through an exposure of aplitic rock from north to south, with 

 a steep westerly dip. It is not unlikely that this vein of gos- 

 san may mark the surface outcrop of a metalliferous vein other 

 than iron. Exploration might reveal the presence of copper 

 sulphides. 



DESCRIPTIONS OF SPECIES. 



ECHINODERMATA. 



Genus ASTRODAPSIS Conrad 



Astrodapsis peltoides, new species 



Plate 2, figure 2 



All of the specimens of this species are of moderate size, 

 suboval or elliptical, moderately elevated, as in Astrodapsis 

 zvhitneyi Remond; ambulacral areas bordered by shallow but 

 distinct grooves, forming narrow ambulacral ridges and dis- 



1 8th Kept. State Min. 1888, p. 530. 



