564 REPORT OF NATIONAL MUSEUM, 1890. 



38385 ; Rocky Hill, Somerset County, New Jersey, 26843 ; York County, Penn- 

 sylvania, 37020; Goose Creek, Loudoun County, Red House, Charlotte County, 

 and Brandy Station, Culpeper County, Virginia, 28116, 73208, and 73215 ; Look- 

 ville, North. Carolina, 73210 ; Forder Saltash, Cornwall, England, 39007 ; Govo 

 Saltash, Cornwall, England, 39008 ; Craig Park, Glasgow, Scotland, 70382 and 

 70384 ; Magdesprung, Wolfshagen, Bodenthal, Blankenburg, Altenbrak, etc., 

 Hartz Mountains, Germany, 36426, 36427, 36428, 36429, 36430, 36431 ; Nassau, 

 Germany, 36420, 36422. 36424, and 36425 ; Anhalt, Germany, 36432 ; Ehrenbreit- 

 stein, Prussia, 36419 ; Nahe, Prussia, 36418, and 36426 ; Steinbach and Berneck, in 

 the Fichtel Gebirge, 36433 and 36434; Boguschowitz, Moravia (teschenite), 

 36529 to 36531 inclusive, and 36533 ; Koditz, in the Fichtel Gebirge (leukophyr), 

 36439 ; Breitenbach, in the Voges Mountains, 36440 ; Hartz Mountains (ophite), 

 6723; Haute Goronne, France (ophite), 36477 and 36478; Beziers, Heranet, 

 France (ophite), 36479; Garraux, Pyrenees, France (ophite), 36480; Champ St. 

 Veron, Brabant, Belgium (Epidiorite), 36370 and 70209; Edinburgh, Scotland 

 (sahlitdiabase), 36441 ; Hof, in the Fichtel Gebirge (proterobase), 36435 ; Baut- 

 zen, Saxony (proterobase), 36436 and 36437; Sperberbach, Hohwald, in the 

 Vosges Mountains (proterobase), 36438. Hammerfest, Province of Finmark, Nor- 

 way (Eukrite), 34828 and 35736. 

 Olivine diabase: Addison, Washington County, Maine, 37019 and 36843; Tenant's 

 Harbor, Knox County, Maine, 39043 ; Auburn, Maine, 28533 ; Lewiston, Maine 

 (very rich in olivine), 37618 ; near Mine La Motte Station, Missouri, 70129 ; Thet- 

 ford Hill, Vermont (drift), 35062 ; Rio Janeiro, Brazil, 69904. 



7. The thkralites. 



Theralite from the Greek word ^pav, to seek eagerly. 



This is the name given by Professor Eosenbusch to a class of intru- 

 sive rocks consisting essentially of plagioclase feldspar and nepheline, 

 and which are apparently the plutonic equivalents of the tephrites and 

 basanites. Eocks of this group are, so far as now known, of very 

 limited distribution. 



The group is founded by Professor Eosenbusch upon certain rocks 

 occurring in dikes and laccolites in the Cretaceous sandstones of the 

 Crazy Mountains of Montana, and described by Prof. J. E. Wolff,* of 

 Harvard University. 



Mineral composition. — The essential constituents as above noted are 

 nepheline and plagioclase with accessory augite, olivine, sodalite, bio- 

 tite, magnetite, apatite and secondary hornblende, and zeolitic minerals. 



Chemical composition. — The chemical composition as given by Mr. 

 Wolff of a sample from near Martinsdale is as follows: Silica, 43.175; 

 alumina, 15.236; ferrous oxide, 7.607; ferric oxide, 2.668; lime, 10.633; 

 magnesia, 5.810; potash, 4.070; soda, 5.68; water, 3.571; sulphuric 

 anhydride, 0.94 per cent. 



Structure. — The rocks are holocrystalline granular throughout. 



Colors. — These are dark gray to nearly black. 



The theralites so far as known have an extremely limited distribu- 

 tion. The group is represented in the collection only by samples from 

 Gordon's Butte, and Upper Shields Eiver basin in the Crazy Mouu- 



" Notes on the Petrography of the Crazy Mountains and other localities in Mon- 

 tana, by J. E. Wolff. Also Neues Jahrb., 1885, i, p. 69. 



