SCIENTIFIC EXPEDITION TO NORTHWESTERN COLORADO 



125 



sage-brush is the characteristic form of vegetation; large grass-covered 

 areas are totally absent, and grama and buffalo grasses do not occur. 



Relation to divide 



Altitude 



Mean annual precipitation 



Percentage during growing season 



Mean annual temperature 



Mean summer temperature 



Mean annual range 



Meeker 



West 



6,182 feet 



16.37 inches 



S3 



43 F - 



64 F. 



46 F. 



The vicinity of Boulder is the meeting-ground of grassland and 

 Rocky Mountain yellow pine (rock pine) formations; Yucca glanca is 

 abundant. There are no oaks, pinyon pines or Utah cedars. At 

 Meeker, sage-brush is dominant over level areas, pinyon pines and 

 cedars on the ridges, and oak along the bases of slopes. There is no 

 Rocky Mountain yellow pine or Yucca glanca, and large grassland areas 

 are totally absent. 



Southern forms have extended farther north in western Colorado 

 than in eastern. Examples of these are Quercus spp., Ephedra anti- 

 syphilitica and Populus uislizeni. The climate of northwestern Colorado 

 is drier from the vegetation standpoint than that of eastern Colorado at 

 the same latitude and altitude, hence southern forms find, on the drier 

 western slope, conditions more nearly like those to which they are 

 accustomed in the hot, arid districts of Arizona and New Mexico. 



Mollusc a Collected in Northwestern Colorado in 1909 

 By Junius Henderson 



An interesting molluscan fauna was obtained. As a supplement 

 to The Mollusca of Colorado is contemplated in the near future which 

 will discuss somewhat fully this fauna, it is thought best at present to 

 give only a list of species collected, as follows: 



Pisidium sp. Thysanophora ingersolli Bland 



Oreohelix cooperi W. G. B. Pupilla Uandi Morse 



Oreohelix haydeni gabbiana Hemph. Vertigo concinnula Ckll. 



