Ihe Relation of Mollusks to Fish in Oneida Lake 267 
Genus Somatroayrus Gill. 
34. Somatogyrus subglobosus (Say). Fig. 45, No. 40. 
Collected at four stations on a sandy shore in shallow 
water associated with (Grillia. This characteristic snail is 
widely distributed from Lake Michigan eastward. Under 
the name of isogonus it is listed by most writers on New 
York mollusks. It is listed under this name by Beauchamp. 
Somatogyrus is eaten by the Common Red Horse. 
Genus Byrninia Gray. 
35. Bythina tentaculata (Linné). Fig. 45, Nos. 22 
Collected at thirteen stations. This snail seems to prefer 
a habitat where the water is in motion; it will thrive equally 
well on the sandy bottom of an exposed or partly sheltered 
bay, in thick vegetation in the outlet (where it was the most 
abundant) or on the stems of such water plants as Water 
Willow, Bulrush or Pickerel-weed (see Chapter III). Rarely 
found on an exposed bouldery point. This abundant species 
was found by Beauchamp at Oswego in 1879 (1886, p. 5). 
Since that time it has been reported from various parts of 
Western New York, principally in the Erie Canal (Walton, 
1891). It was observed in Lake Michigan by the writer in 
1893 (Baker, 1902, p. 330) and has been recorded from 
Michigan, Wisconsin, and Ohio. It has been thought to 
have been introduced from Europe but its wide distribution 
and great abundance point to its being a native species 
inhabiting both continents, like Galba palustris, Margaritana 
margaritifera, and ITelix nemoralis. It is eaten by the 
Pumpkinseed. 
It has been observed on the following plants: 
Pickerel-weed (Pontederia cordata). On stem. 
Water Willow (Dianthera americana). On stem. 
American Bulrush (Scirpus americanus). On leaf. 
Lake Bulrush (Scirpus occidentalis). On leaf. 
White Water Lily (Castalia odorata). On stem. 
Yellow Water Lily (Nymphaa advena). On stem. 
Fig. 44. Lampsilis borealis. 1, 3. males; 2, 4, females. 
