The Productivity of Fish Food in Oneida Lake 169 



foot of water, sand bottom in four and a half feet of water, 

 and mud bottom in 18 feet of water. It was most abundant 

 on a rocky shoal in water a foot deep, a single boulder having 

 54 spec:imens. 



*55. Amnicola bakeriana Pilsbry. 



This new Jiiuiicola (Pilsbry, '17a, p. 44) is one of the most 

 abundant species of the genus. Its turreted shape, elongated 

 spire, and deep-sutured whorls differentiate it from related 

 species. I1ie spire varies much in length and the whorls in 

 obesity and there are forms which are difficult to separate from 

 elongated individuals of the form nimia. It occurs on all 

 varieties of bottom, though less numerous on boulder and most 

 abundant on sand, clay, and mud bottoms, where there is a 

 heavy growth of algae {Cladophora or CEdogonium). Three 

 individuals were found on a leaf of Sagittaria arifolia. In 

 depth this species is most abundant in water 3-6 feet deep and 

 it occurs from i to 18 feet deep. It was dredged in great 

 abundance on a mud bottom covered with the alga Cladophora 

 fracta in 8J/2 feet of water. At this time of year many imma- 

 ture individuals occurred with the adults. Bakeriana was 

 observed in the 191 5 collections from the following habitats, 

 mixed with limosa (Baker, '16, p. 268). Frenchman Island, 

 No. 217-p; Shepard Point, No. 225-c; Muskrat Bay, No. 

 247-b ; Thierre's landing, Lower South Bay, No. 280-e. 



*56. Amnicola bakeriana nimia Pilsbry. 



One of the commonest varieties of this genus is a small form 

 in which the whorls are more or less tumid below the suture, 

 the spire is depressed, and the body whorl is swollen, giving 

 the whole shell a wide appearance. A large specimen measures 

 3j% mm. in length. It occurs on all kinds of bottom in water 

 from 1-18 feet deep, being most abundant on sandy clay or mud 

 bottoms covered with algae in 1-4 feet of water. About 10 per 

 cent of the individuals collected were immature. A single 

 specimen Avas collected from a leaf of the Arrow-head, 

 Sagittaria arifolia. This form was observed in one lot of 

 Amnicola limosa from Frenchman Island, collected in 191 5 

 (No. 220-d). 



