•70 GEOLOGICAL BIOLOGY. 



formation in western New York is calcareous and finely argil- 

 laceous; in eastern New York the same formation is arena- 

 ceous and flaggy ; although representing the same formation, 

 one may be called the argillaceous or calcareous facies, and 

 the other the arenaceous facies, of the Hamiilton formation. 



Area, Province, Region. — Again, the terms area, province, 

 region, when applied geologically, refer to the geographical 

 districts in which there was greater or less uniformity in the 

 kind and succession of sedimentation for a given geological 

 period. Thus, the Appalachian province or the Mississippian 

 province may be spoken of. These same terms when used in 

 zoology or botany refer to the districts which, separated by 

 more or less sharp physical boundaries, are characterized by 

 distinct faunas or floras. 



Geological Range and Geographical Distribution. — A conven- 

 ient distinction may be drawn in the usage of the terms range 

 and distribution, which are now almost synonymous. In 

 speaking of the separation of species, or genera, or faunas, or 

 floras, when separated in space, distribution will be used ; when 

 separated in time, range. Thus, according to Ulrich, the 

 Vitulina fauna of the Middle Devonian may be said to have a 

 distribution limited to South and North America and Africa; 

 its range is Lower and Middle Devonian. 



Variations and Mutations. — Waagen has proposed to dis- 

 tinguish the changes of form observed on comparing the same 

 species from different places. When the specimens compared 

 belong to the same geological horizon, but come from the 

 same or different geographical areas, the differences of form 

 are called variations ; when the specimens come from different 

 geological horizons, thus representing time-range, the differ- 

 ences of form are called mutations. 



Development and Evolution. — Another analogous distinction, 

 which is explained more fully elsewhere, is observed in the 

 restriction of the term development to the processes of expan- 

 sion of characters of the individual in ontogenetic growth, 

 and the term evolution to the changes expressed in the indi- 

 viduals succeeding each other in phylogenetic succession. 



Initiation and Origin, — Another distinction, in the way of 

 greater precision, is in the use of the term initiation in place of 



