Fnik : LICHENS OK THE MINNESOTA \ALI.EV. 297 



Closely related to the above formations are two occupying 

 the same areas and named for a lichen almost wholly confined 

 to them. They follow below : 



Lccanora calcarca contorta lichen fo?-ination of exposed lime- 

 stone pebbles (Granite Falls). 



Placodium vitellinum (Ehrh.) Na?:g. and Hepp. var. aurel- 

 lum Acii. 



Lecanora calcarea (L.) Sommerf. var. contorta Fr. 



Lecanora privigna (Acii.) Nye. 



Lecanora privigna (Acii.) Nye. var. pruinosa Auct. 



Endocarpon pusillum Hedw. 



Verrucaria muralis Acn. 



Staurothele diffractella (Nye.) Tuck. 



Like the last, this formation is not well developed in other 

 studied portions of Minnesota, and I shall give the similar one 

 for Fayette, Iowa, for comparison. 



Lccanora calcarea contorta lichen formation of exposed li?ne- 

 stone pebbles (Fayette, Iowa). 



Placodium cinnabarinum (Ach.) Auz. 



Placodium vitellinum (Ehrh.) Naeg. & Hepp. var. aurellum 

 Ach., C. 



Lecanora muralis (Schrev.) Schaer. var. versicolor Fr. 



Lecanora calcarea (L.) Sommerf. 



Lecanora calcarea (L.) Sommerf. var. contorta Fr., C. 



Lecanora privigna (Ach.) Nye., C. 



Rinodina bischoffii (Hepp.)Koerb. 



Biatora russellii Tuck. 



Endocarpon pusillum Hedw., C. 



Verrucaria nigrescens Pers. 



Verrucaria muralis Acii., C. 



Lichens common to the two formations are marked (C) in the 

 Fayette list, and comparison shows marked similarity in the two 

 formations about 200 miles distant, except that the latter is con- 

 siderably better developed than the former. This is as would 

 be expected when we consider that the Iowa region is one where 

 limestones abound, while the Minnesota is one in which the 

 limestone pebbles are those transported in glacial drift and are 



