No. 499] 



DWARF FAUNAS 



485 



illustrated by one layer which is brown and impure, in- 

 dicating deposition in shallow and turbid water. In this 

 layer the brachiopods are especially small and depau- 

 perate. Productits cora rarely reaches one inch in 

 diameter and the Rhynehonellas are minute. The pelccy- 

 pods are very abundant but dwarfed. 



2. The influence of the formation of the beds of gypsum 

 and gypseous mails at the time these limestone reefs 

 were growing. Dawson ascribes the formation of these 

 gypsum deposits to chemical change produced on the 

 calcareous beds and reel's by contact of streams charged 

 with H 2 S0 4 . Such streams are easily accounted for by 

 the volcanic activity known to have occurred in this region 

 while the shell beds were growing. The great amount of 

 C0 2 released in the change from calcareous carbonate to 

 gypsum would surely render unfavorable the water in 

 which these limestone-secreting animals were living. 



e. De Lapparent attributes the depauperized fauna of 

 the Mediterranean in part to the greater preponderance 

 of CO. in the water of that sea over that of the Atlantic. 



One of the most notable facts arising from a study of 

 red strata is the very frequent total absence in them of 

 all fossils and the often dwarfed and impoverished faunas 

 of the associated strata of other colors. Such red beds 

 are especially conspicuous in the rocks of the Devonian, 

 Permian and Triassic eras. Geikie mentions that fossils 

 are practically absent from the red strata of the Old Red 

 sandstone of England, but abound in the gray or black. 32 



According to the same author 33 " the impoverished 

 fauna of the Permian rocks of central Europe is found 

 almost wholly in the limestone and brown shales, the red 

 conglomerate and sandstone being, as a rule, devoid of 

 organic contents." 



In speaking of these same rocks de Lapparent 34 says 

 that "in northern Europe the mollusks of the upper 



