FRESH WATER FAUNA. 167 



rocks. Their mode of oecurreuce everywhere .sho\v.s e^■idellce of shallow 

 Wiiter, but they rapidly pas.s into beds iudieating much deeper water. 

 Associated with these fresli-water shells are iiuiuerovis frajiiiieiits of })lant 

 remains, proving, without doubt, the existence at no great distance of ii 

 land surface. The specific characters of these shells will be found described 

 el.sewhere by Mr. Walcott.' 



Limestone of Richmond Mountain.— Between Eureka CauAdn and Richmond 

 Mountahi lies a body of limestone uniformly inclined to tlie east until it 

 pa.sses beneath tlu' andcsites of the latter mountain. It rises nearly 700 

 feet above the valley, with a fairly regular slope, except where trenched by 

 short (h'ainage channels which have cut deeply into the rock, giving the 

 ridge a somewhat ribbed appearance. The beds strike N. 1G° E. and 

 dip from 40° to 50° under the lavas. The Richmond Smelting Works are 

 situated near the northei-n end of this limestone body. Just back of the 

 smeltei's the base of the limestones -a*©- well exposed, and near the rail- 

 way cut there maj- be seen a good exposure of strata. At the base of 

 the cliff occurs a series of dark argillaceous shales of unknown thickness 

 weathering on exposure to blue and gray clays. In these clays may be 

 lound indications of plant remains associated with the Physa prisca and 

 Amimlaria obtained on the opposite side of the ravine in New York Hill, 

 the shells serving to correlate the beds. It is to be regretted that their 

 strike and dip could not be determined with precision, but they "give every 

 appearance of passing conformably beneath the overlying strata. 



The following sectiijn was made across the strata extending from the 

 top of the series down to the clay beds at the base: 



Feet. 



1. Coarse conglomerate cemented in fine arenaceous grains 50 



2. Compact gray and yellow sandstones carrying a little calcareous material, 



aud occasional tlun belts of limestone 200 



3. Fine smooth pebbles in a yellow matrix 10(» 



■1. Brownish wliite sandstone 200 



5. Fine conglomerate, with an admixture of calcareous material throughout. 100 



6. Gray limestone, passing into a liglit gray and yellowish sandstone 75 



7. Cherty limestone, passing into fine siliceous limestone 75 



8. Light colored aud banded vitreous tpiartzite 25 



' Paleontology of the Eiirekii District, Mon. vm. U. S. Ueological Survey, \y. 261. 



