384 The American Naturalist. [April, 
` tal were found the two new pyramids 4P and iP. The axial ratio of 
these crystals is 1: .61775.. The author has also made a crystallo- 
graphic examination of the monazite occurring so abundantly in the 
Brazilian granites and gneisses. The crystals of this substance are 
always tabular parallel to « Pæ. They contain the same forms as 
do the Ilmengebirge crystals, but are never twinned. Upon washing 
a portion of sand from Bohia a 3 mm. long crystal of euclase was 
obtained whose density is 3.1. It is very rich in planes, being pos- 
sessed of not less than three prisms, six clinodomes and three negative 
pyramids, beside the clinopinacoid. 
Mineralogical Notes.—Christianite crystals are reported by 
Gonnard” as lining geode cavities in the basalts of dykes at Quey- 
riéres and Fay le Froid, Haute Loire, France. In the latter case the 
christianite groups enclose many crystals of augite. The trachyte of 
Montcharet, occurring as a dyke in granite, is cut’ by fissures whose 
walls are lined by chabasite.* The cubic faces of galena crystals 
implanted in druses of quartz at Pontgibaud are roughened by little 
cavities whose walls have the positions of octahedral planes. The 
phenomenon is regarded by Gonnard" as the result of corrosion. The 
same author mentions the existence of large crystals of beryl in the 
granites of Droiturier, near La Palisse, Allier, psilomelane in mam- 
millary forms at Croix Moraud, Mt. Doré, and cubic pseudomorphs of 
artz after some unknown mineral, probably fluorite, in the vicinity 
of d’Aubenas, Ardéche. 
Three specimens of melilite from Mt. Somma, with densities of 2.917, 
2.932 and 2.945 respectively, were powdered, purified, and analyzed by 
Bodlander” with this result : 
SiO, AlO, FeO, CaO MgO K,O NaO H,O Total 
41.34 10.37 429 33.84 5.79 113 3.45 .08 — 100.29 
The author combats the view of Vogt that melilite is an isomor 
phous mixture of the gehlenite and akermanite molecules. He thinks 
that the negative variety is an admixture of R”SiO, and the alumin- 
ate R”,0,R”, while the positive variety is a compound of the same 
silicate with the aluminate R,’”O,R,”. Intermediate varieties are iso- 
morphous mixtures of these. 
“Bull. Soc. Franç d. Min., 1892, xv, p. 28. 
“by p. 31. 
MTb., p. 34. 
Neues. Jahrb. f. Min., ete., 1893, i, p. 15. 
See 
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