June, 1919] 



Fauna of Rock Bottom Ponds 



435 



In one littoral situation, stony and with abundance of fila- 

 mentous algas, there were twenty-five PhyscE in an area 6x4x5 

 inches. In another somewhat similar situation there were 

 fifty-one in a space 2x5x3 inches. Most of them were young 

 which was also true of those found in the algas at Station 1. 

 Noto?iecta were likewise common. 



Station 3. This was 500 hundred feet distant from Station 1 

 and covered that portion of the pond farthest away from the 

 region of the original pool. It was one of the last portions to 



Station 3 of Pond I. 



be covered with water. The sides of the quarry rose up twenty- 

 five feet and as elsewhere they were entirely devoid of vegetation. 

 The conditions are shown in photograph above. 



The water was not more than eighteen inches deep. In it 

 there was a rich growth of filamentous algae from bottom to 

 surface. That on the surface formed a thick mat which in 

 places extended twenty-five to thirty feet out from shore. It 

 was more abundant here than anywhere else in the pond. 

 On the bottom there was an inorganic sediment, chiefly quarry 

 dust, one-eighth of an inch thick. Dead and decaying algae 

 were establishing the beginning of an organic deposit. In 

 some places the partly decomposed algal material was a quarter 

 of an inch thick. This amount, of course, would tend to diminish 

 as decomposition became more complete. 



