122 Wisconsin Academy of Sciences, Arts, and Letters. 
within a meter of the shore. At a distance of 50 or 60 meters from 
shore there is a succession of sand bars representing present and 
former breaker lines, which run parallel with the shore. 
The transition from gravel to sand shore is in some places well 
marked and in others is almost imperceptible. Usually, pebbles 
and large stones gradually become less in number until they finally 
disappear. In the coves and bays, especially in the area between 
Fox River and Long Point Island, there is little fine gravel and no 
coarse gravel, all is fine sand of even texture. Sand bottom areas 
are usually shallow near shore (out to 150 meters) the depth sel¬ 
dom exceeding one meter. In the protected bays, and even on the 
more exposed shores, vegetation is abundant and varied, including 
both submerged and emergent species. In two habitats the sand 
was mixed with marly clay and Chara was abundant. Filamentous 
algae (Cladophora, etc.) are usually abundant. A sand bottom 
unbound by vegetation is generally a poor faunal habitat, the 
shifting character of the substratum burying the biota and smoth¬ 
ering it. Some Naiades, however, prefer this kind of a habitat and 
are found abundantly in such places. 
Mollusca are abundant in many of the habitats. Curiously 
enough, the Naiades, which are fairly common on gravel and 
boulder bottoms, occur sparingly on the sand bottom area, 
Sphaerium is rare and Pisidium not as abundant as on the gravel 
bottom. Of gastropods, Somatogyrus forms 22 per cent, Amnicola 
limosa porata 18 per cent, and Planorhis parvus and Valvata tri- 
carinata each 8 per cent. Pisidium constitutes 12 per cent. As a 
whole, the molluscan fauna of the sand bottom is richer in species 
than the gravel bottom, increasing from 35 to 40. The presence of 
filamentous algae on the higher plants accounts in large measure 
for the abundance of some of the mollusks, as the Amnicolidae and 
Valvata. 
The associated animals outnumber the mollusks about two to 
one. The most abundant being Hyalella (about 18 per cent) and 
Chironomid larvae (25 per cent). Oligochaete worms (mostly 
Stylaria) make up about 14 per cent. Trichoptera comprise six 
groups, Agraylea, Molanna, Oecetis, Helicopsyche, Polycentropidae, 
and a few Leptocerids. Ephemeridae includes nymphs of Caenis, 
Ephemera, and Ephemerella. Acarina is represented by five 
genera, Limnesia, Limnesiopsis, Piona, Unionicola, and Hydrachna, 
Piona being the most numerous. Hemiptera includes nymphs of 
Belostoma, adults of Plea striola, and a Corixid nymph which was 
