336 The American Naturalist. [April, 



This phenomenon leads the author to the assumption that eudialite 

 and eukolite are the end members of an isomorphus series, of which 

 the isotropic substances intermingled with the eudialite are interme- 

 diate members. Ainigmatite is found only in the peripheral masses as 

 allotriomorphic grains with a pleochroism A = black > B = brown- 

 red > C = carmine. One of the new minerals occurring in the 

 coiir-t-irniiiicii mck has the composition: 



It is isotropic or weakly doubly refracting. It shows no cleavage, 

 is hard, and has a density of 2.753. Its color is light-red except in 

 certain star-like areas where it is more deeply colored. It is one of 

 the youngest of the rock's components. In the normal rock these 

 constituents are so aggregated as to produce the trachytic structure. 

 In the peripheral varieties aegirine, nepheline and the feldspar- are in 

 two generations. These minerals and eudialite occur as phenocrysfc 

 in a fine-grained green ground mass of the first three mentioned com- 

 ponents, sodalite and the new minerals above referred to. The struc- 

 ture of this aggregate is intermediate between the hypidiomorphic and 

 panidiomorphic. A dyke eleolite syenite from the same region has a 



thoroughly panidiomorphic ground mass. In the course of 



a very exhaustive geological article on Mite Vulture, in Basd- 

 icata, Italy, Deecke 1 describes the products of the volcano as 

 lavas and tufas. The former, with the exception of the hauyne- 

 trachyte of Melfi, all possess a similar appearance. They are 

 dark, compact or slaggy rocks with phenocryst- 



a ground mass of leucite, nepheline, feldspar, augite, biotite, melilite, 

 containing sometimes olivine, garnet, apatite and magnetite. The 

 augite is in well formed idiomorphic crystals, both in the lava- and « 

 the tufas. These are zonal with a yellow augite surrounded by a 

 greenish zone, the material of which also separates as small crystal! !11 

 the ground mass. The hauyne is the next component in abundance. 

 It possesses the usual characteristics of this mineral, and alters into 

 zeolites, of which the most important is natrolite. The leucite, nephe- 

 line, plagioclase and sanidine are usually in such small grains as to be 

 visible only under the microscope. The latter mineral occurs also as 

 an essential constituent in 1 cm. long crystals in the phonolite ot 

 LeBraidi, East of Melfi, and in some of the tufas. Olivine is found 

 'Neucs. Jahrb. f. Min., etc., B. B. vii, p. 556. 



