CLASSIFICATION OF IGNEOUS ROCKS 177 



(2223) Nephelite-monzonite. Under this name Lacroix^ de- 

 scribed rocks from Madagascar consisting essentially of anortho- 

 clase, basic labradorite, nephelite, titaniferous pyroxene, bark- 

 evikite, titaniferous magnetite, and apatite. The mineral pro- 

 portions are quite variable. To make it conform with the usual 

 monzonite group, the term nephelite-monzonite is here adopted for 

 a nephelite rock of Class 2 with acid plagioclase about equal in 

 amount to the other feldspars. The rock described by Lacroix 

 is included under the calci-nephehte-monzonite family. 



Nephelite (leucite-)latite. The extrusive equivalent of 

 the preceding. 



(2224) Nephelite- (leucite-)monzodiorite. A term here sug- 

 gested for nephelite-(leucite-)bearing rocks comparable to grano- 

 diorites among the quartz-bearing. 



(2225) Nephelite- (leucite-)diorite. A term, analogous to 

 nephelite-syenite, here suggested for nephelite-acid plagioclase 

 rocks. Under this family would fall Adams and Barlow's^ rag- 

 lanite, an abnormal rock on account of its large content of 

 corundum, 4.45 per cent. Since it carries only 12 per cent by 

 weight of nephelite, it is also far from the center point. 



Nephelite- (leucite-)tephrites and nepheHte-(leucite-) 

 basanites belong here in part. 



(2229) No plu tonic rock has been located in this family, but 

 there is an extrusive, a leucite-tephrite from the Roman Comag- 

 matic region, described by Washington.^ 



(2230) A leucitite from the Roman Comagmatic region, de- 

 scribed by Washington,'' is the only rock yet found here. 



[To be concluded] 



^ A. Lacroix, "Sur les granites et syenites quartziferes a aegirine, arfvedsonite 

 et aenigmatite de Madagascar," Compies Rendus, CXXX (1900), 1208; also "Sur 

 la" province petrographique de Nord-ouest de Madagascar," ibid., CXXXII 

 (1901), 439. 



^ Frank D. Adams and Alfred E. Barlow, "Geology of the Haliburton and Ban- 

 croft Areas, Province of Ontario," Mem. Geol. Surv. Canada, No. 6 (1910), p. 314. 



3 Henry S. Washington, "The Roman Comagmatic Region," Carnegie Publica- 

 tion. No. 57 (Washington, 1906), p. 73. 



■* Ibid., p. 136. 



