1914J 
Jackson: Land Vertebrates of Ridgeway Bog 
17 
the more dominant species and those which distinctly characterize 
associations are mentioned. 
1. The Aquatic Association. The liiota of the area covered 
permanently by water is included in the Aquatic Association. 
Were we to consider the entire fauna and flora of this area it 
would then be well to raise it from the rank of an association to 
lliat of a formation^ since the plants and animals, other than 
Fig. 2. A Portion of the Aquatic and Sedge Associations, Showing 
IN Extreme Distance the Cassandra and Tamarack-Spruce As- 
sociations. 
terrestrial vertebrates, found in this habitat are vastly different 
from those in the other parts of the bog. The characteristic 
plants are Potamogeton 7iatans and Nuphar advena; a few Typha 
latifolia invade from the Sedge Association (fig. 2). Rana sep- 
tentrionalis^ and Chrysemys hellii are the most characteristic 
* an ecological formation I mean an ecological unit composed of closely related ecologi- 
cal associations. Formation is here used as a more general term than association. Format io''s 
differ more widely from each other than do associations. (Flahault and Schroter, 1910, pp. 5-8, 
25-28.) 
® The northern frog, Rana septentrionalis, has been considered by some herpetologists to l)e 
a subspecies of Rana clamitans; specimens of the two forms are often morphologically very simi- 
