22 SAND DUNE REGION OF SAGINAW BAY. 



here are a few leopard and green frogs, deer mouse and Baird's field 

 mouse, but as a whole the fauna is very poor owing largely to the 

 drifting sand that soon buries the logs. Where the beach is partially 

 protected from the waves by off-shore bars and is thus narrower, the 

 upper part is damper and more protected from shifting sand. Here a 

 few sedges and certain forms such as various snails (see Baker) are 

 found among the logs. The characteristic forms of the dune face are 

 the grasshoppers (see ShuU). 



The conditions described above are typical of the beach throughout 

 most of the region, but there are a few local variations that should be 

 mentioned here. These variations are associated with the sand flats 

 that are being formed back of the sand bars at Hat, Oak and Little 

 Oak Points, and at the end of Sand Point. These flats are moist sand 

 and support a sparse vegetation of sedges, Equisetuvi, nodding ladies 

 tresses, etc., and where broader are covered with clumps of willows, 

 balsam-poplar, and occasionally paper birch. (Plates II, -III a.) 

 There is apparently no characteristic fauna on these flats, the inhabi- 

 tants being the beach forms plus a few swamp types (e. g. Jefferson 

 salamander, leopard frog, cockroaches, myriapods, etc.) and in the 

 drver places with some from the ridges (skink, fox snake and milk 



snake). 



When these flats are formed or when an off-shore bar has become 

 elevated to enclose a lagoon (Plate II b), the older beach is removed 

 from wave action and becomes a fossil beach. The best fossil beach 

 was found at the end of Sand Point, and was so recent that it was still 

 strewn with logs in advanced stages of decay (Plate TV a). The 

 fauna consists of the upper beach forms with a few others from the 

 sand region that seem to find particularly favorable conditions here. 

 The conspicuous forms are: Baird's mouse, deer mouse, skink, fox 

 snake and milk snake, and a number of invertebrates (such as cock- 

 roaches, myriapods and snails) that are usually found in decaying 



logs. 



Wooded Sivamps: The habitats grouped here vary greatly. In 

 one direction they grade into the grass marshes, in another into the 

 low sand flats that occur between the ridges when the elevation is 

 somewhat higher, and in still another into the mesophytic forest. The 

 flora of the typical swamps of the wetter type in the sand region con- 

 sists principally of a groA^ih of swamp white oak, black ash, red maple, 

 arbor vitae, yellow birch and a number of ferns and mosses. As these 

 swamps approach those of the grassy type they become mixed with 

 willows, alder (.4. incana), dogwoods, and cottonwood. While in the 

 hio-her swales the American aspen, paper birch, balsam-poplar, etc., 

 become predominant. 



