144 College of Forestry 
detritus covering on the bottom while the large bivalves, 
owing to the position which they assume (the siphons in the 
water above the bottom), must take their food from the water 
and this probably consists of dust-fine detritus held in sus- 
pension and some plankton. Laboratory experiments, ex- 
tended field observations and stomach examinations will be 
necessary to provide a body of facts in support of these 
inferences. 
III. Recorps or OTHER OBSERVERS ON THE VEGETABLE 
Foop or Mo.uuusks. 
Records of the use by mollusks of definite species of plants 
are rare, most statements simply asserting that mollusks 
feed or rest on plants. A few of these more definite state- 
ments appear below. 
Hankinson (1908, p. 235) states that in late spring the 
following snails were collected from algze, chiefly Vaucherva. 
Valvata tricarinata Say. Planorbis parvus Say. 
Amnicola limosa Say. Pisidium sp. 
Moore (1915, p. 284) found Ancylus on two species of 
Pond-weed, Potamogeton americanus and P. amplvfolius. 
The statement is made. (p. 285) that ‘The Mollusca — 
Planorbis, Iamnea, and Physa— were common on all of the 
Potamogetons.” 
Walker (1896, p. 97) records an abundance of small mol- 
lusks as living in a thick bed of Chara, at High Island, near 
Charlevoix, Mich. A single haul of the dredge brought up 
several hundred specimens, embracing 26 species belonging 
to 7 genera as noted below: 
IGYIMMBA CATR, lee eke nese eicdeleciae eee 5 species 
(Bilan ones: tir ethens etdercisas > nies Re 3 < 
IPD Sais errons weiss acre cll ease eae 1 od 
Walliviaitaaacien.c yaar cote eehS cote OR eae 2 es 
JAmTitcola: take. See, od Woe 3 a] 
Bythinellasy seems iesis oe Eee 1 4 
Pisvdiumeeys seeusee = - Be ne 5 a 11 sf 
ROGAN SARI. is eel ne serene ede 26 fF 
