ACADEMY OF NATURAL SCIENCES. 291 



It is evident that the formation consists of beds of iron pyrites (mundic) 

 with a small but variable portion- of copper pyrites, and that the rusty, upper 

 portions are due to the gradual decomposition of the sulphurets above the per- 

 manent water-line, or where the atmosphere has had access. Below the water- 

 line we may not expect to find the rusty ochrey slates. This is shown, also, at 

 a shaft which has reached the water. Blocks of mundic, taken out of that shaft, 

 are interstratified with talcose slate. At one point, in the bottom of the quarry, 

 a layer of green and blue carbonate of copper is found, and this is evidently the 

 result of a gradual concentration of the copper from the decomposed ground 

 above. The soft slate, as quarried, is trammed to a five-stamp mill, with very 

 coarse grates, and nearly forty tons are run through it daily. The pay is said to 

 vary from two to twenty dollars, but the average is reported to be from five to 

 six dollars per ton. 



Mr. Stearns read the following : 



Since my communication to the Academy of date July 16th last, on the 

 Shells of Baulines Bay, additional specimens (4) of Haliotis rufescens have 

 been found by Mr. Harford and Dr. Kellogg ; also many specimens of Kather- 

 ina tunicata, and one of Blopalia Hindsii ; from between the umbos of very 

 large specimens of Mytilus Californianus, collected by the same gentlemen, 

 several specimens of Barleia 1 subtenuis Carp. 



In addition to the above marine forms, the following species were found by 

 the same parties in a gulch at Belvidere Ranch, not far from Capt. Morgan's 

 house, south side of Baulines Bay : Helix Nickliniana, H. arrosa, H. infumata, 

 H. Columbiana (hirsute var.) and H. Vancouverensis. Also, near a small 

 stream on the same ranch, Bythinella Binneyi, Tryou. The last named species 

 had previously been found in this neighborhood by Rev. J. Rowell. 



Prof. Blake mentioned that a tooth of a mastodon had been 

 found about three miles from Antioch, near Monte Diablo, by Capt. 

 Stevens. 



Mr. Stearns gave an account of the Helix, its anatomy, geo- 

 graphical distribution, and use as an article of food and for medi- 

 cinal purposes, in both ancient and modern times. 



Prof. Blake stated that he had in his possession a portion of a 

 human skull said to have been taken from a depth of 250 feet 

 below the surface, near Columbia, in Tuolumne County. 



