496 PETROLOGICAL ABSTRACTS AND REVIEWS 



generally contains plagioclase, is always richer in hornblende, and has part of 

 the nephelite changed to analcite. The unfortunate usage of giving locality 

 names to new rock types is ever a cause for confusion. Shotdd the original 

 definition be considered the standard, or must a rock possess every accessory 

 of the original rock to be of the same type, that is, should the words of the 

 definition or the rock from a certain locality be the standard ? If the latter, 

 then practically every outcrop shoiild have a new name, for slight variations 

 wUl always be found. 



Lacroix, a. "Les syenites a riebeckite d 'Alter Pedroso (Portu- 

 gal), leurs formes mesocrates (lusitanites) et leur transforma- 

 tion en leptynites et en gneiss," Comptes Rendus, CLXIII 

 (1916), 279-84. 



Under lusitanite, after the name of the country where found, there is des- 

 cribed a mesocratic riebeckite-aegirite-syenite. Where new names are based 

 upon variations in the mineral percentages, modal percentages should be given. 



Lacroix, A. "Les laves a hatiyne d'Auvergne et leurs enclaves 

 homoeogenes," Comptes Rendus, CLXIV (191 7), 581-87. 



Ordanchite is applied to certain hauynite-tephrites from la Banne d'Or- 

 danche. Phenocrysts of plagioclase (" oscillent entre le labrador et 1 'andesine ") , 

 blue hauynite, more or less corroded hornblende, and augite are visible to the 

 unaided eye. Microscopically there are seen in addition titaniferous magnetite, 

 titanite, apatite, and rarely olivine. Tahitite, after its occurrence on Tahiti, 

 is a lava resembling ordanchite but more alcalic. Lacroix considers it a micro- 

 litic form of nephelite-monzonite. It contains phenocrysts of hauynite in a 

 vitreous groundmass of microlites of augite, titaniferous magnetite, hauynite, 

 and perhaps a little orthoclase and leucite. Mareugite is a name given to a 

 medium-grained rock from Mareuges, Auvergne, which contains 60 per cent 

 light minerals (bytownite and hauynite). The dark minerals present are not 

 mentioned, but in an associated rock, called type two, they are hornblende, 

 augite, titaniferous magnetite, and a little blue hauynite, and therefore they 

 apparently also occur in the mareugite. 



Lacroix, A. "Les laves leucitiques de la Somma," Comptes Ren- 

 dus, CLXV (191 7), 481-87. 

 Vesuvites are the leucite-tephrites from Vesuvius. Four apparently new 

 analyses are given. Nine analyses of "ottajanites" are also given. They 

 contain more plagioclase and less leucite than the vesuvianites, but since no 

 proportions are given the dividing lines cannot be stated. Terms such as more, 

 less, little, and much are of no value for comparison. 



