

204 



LIFE OF THE PLEISTOCENE 



direction practically parallel to its present course, as shown by the direction 

 of the oblique lamination of the strata. A change of the river's course, such 

 as cutting across the neck of an 'ox-bow,' or some similar shifting, left the for- 

 mer bed at this point a lagoon, similar to the so-called 'sloughs' of the Missis- 

 sippi River. A lagoon of this nature, while it quickly becomes dammed at the 

 up-stream end, for a time receives a portion of the current in time of high water. 

 In the case under consideration, the layer of red, more or less arenaceous, clay 

 was probably deposited during this period of partial isolation. Further separa- 

 tion of the slough from the stream is effected by the growth of willows and other 

 vegetation upon the alluvial ridge at its head, which rapidly gains in height 

 by the debris collected thereby. The lagoon thus formed is a very favorable 

 station for molluscan and other aquatic life, sedentary animals, or those of 

 weak locomotive powers becoming far more numerous than in the active current 

 of the parent stream. Such a lagoon thus gradually fills up with fine mud 

 partly composed of organic material. In the case under consideration, the 

 black clay represents this period. Finally the lagoon or 'slough' became dry 

 land, this being the ordinary result of the process. The naiad fauna of the 

 Fish-house Deposit is precisely similar in general character to that of the 

 'sloughs' of the Mississippi River today. " 25 



ii Life of the Fish-house Clay 



Plants 26 

 Coniferous and deciduous wood represented by plant stems and seed. 

 Birch (Belida) Maple (Acer) 



Pine (Pinns) Basswood (TitiaHubid) 



Oak (Quercus) Gum (Nyssa biflora) 



Animals (Mollusca) 27 



Alleged allied living forms 



subrotundus Lea 



rectus Lam. 



anodonloid.es Lea 



corpulenta Cooper 



Fish-house species 

 Unto subrolimdoides Lea 



" rectoides Whitfield 



" praeanodontoides Whitfield 

 Anodonta corpulentoides Lea 



Present habitat 

 Mississippi drainage 



" grandioidcs Lea 



Unio ligamentoides Lea 

 " alatoides Lea 



grandis Say 



ligamentinus Lam. 

 alatus Say 



Mississippi and St. Law- 

 rence drainage 



" humerosoides Lea 



complanahts Sol. 



Atlantic and St. Law- 

 rence drainage 



radiatoides Lea 



radiatus Lam. 





25 Pilsbry, op. cit., pp. 568-569. 



28 Woolman, op. cit., p. 211; Berry, Torreya, VII, pp. 80-81; X, pp. 260-261. 

 27 Woolman, op. cit., pp. 211, 208. The writer has rearranged the habitats to correspond 

 with the present knowledge. The old nomenclature is used. 



