xl. ABSTRACT OF PROCEEDINGS. 



Rank II. Based on similarity of principal mineral con- 

 stituents. Produces 7 Sections, e.g. granitic, gabbroic, 

 theralitic, etc. 



Rank III. Based on community of origin from similar 

 parent magmas. The latter are defined by the presence 

 of certain index minerals in the consolidated rocks, (e.g. 

 a granite, a granite-aplite, and a rhyolite, etc. may all be 

 derived from one magma ; other granites, rhyolites etc. 

 will be derived from similar magmas). Produces 12 Orders, 

 e.g. granates, essexates, etc. 



Rank IV. Based on habit of mass. Produces 7 families 

 in each order, e.g. granophites, dioromicrites, gabbrolavites 

 (basalts), etc. 



Rank V. Based on nature of minor mineral constituents. 

 Produces a number of genera in each family, e.g. muscbi- 

 granophite, anaugi-hyper-peridotite (harzburgite). 



Rank VI. Based on texture, but to be applied only in 

 families where there is much variety of texture. Produces 

 Sub-genera, e.g. spheri-mono-rhyolite, graphi-bi-rhyolite, 

 etc. 



The system of nomenclature described is an elaboration 

 of that already proposed by the author in a preliminary 

 paper in the Geological Magazine (1901). 



The desiderata of a systematic nomenclature are as 

 follows: — (1) Each name should indicate the rank of the 

 group to which it belongs. In the system proposed names 

 of series end in -ane, of sections in -ote, of orders in -ate, 

 and of families in -ite. Genera are shewn by the presence 

 of a mineral prefix and sub-genera by a textural prefix. 

 (2) Each name should indicate the feature which dis- 

 tinguishes the group from others of the same rank. This 

 is not necessary in the higher ranks, but is accomplished 

 for families, genera, and sub-genera. Thus a suffix, as 



