the present survey seem to support both these state- 

 ments. The monthly distribution of this species has 

 been already discussed. 



Bigelow (1922) found that D. pulex was not pres- 

 ent in any of the Cisco stomachs from the eastern end 

 of Lake Erie, but that it formed the bulk of the food 

 of the ciscoes in the western portion of the lake dur- 

 ing summer and autumn. It has been identified also 

 in the stomach contents of the mooneye, carp, carp 

 sucker, silverside, green -backed shiner, Cayuga 

 shiner, sand -roller, white bass, yellow perch, log 

 perch, and lake sheepshead. The fact that it is 

 eaten by so many and such different fish is another 

 convincing testimony of its value as a fish food. 



54. Diaphanosoma brachyurum (Lieven). Found 

 at 4 marginal stations on the Canadian shore and 5 on 

 the American shore. Eaten by the cisco. 



55. Diaphanosoma leuchtenbergianum Fischer. 

 Found at 16 of the marginal stations including all 

 those at the western half of the lake on both sides; 

 frequently very abundant. It was found in small num- 

 bers at various stations scattered through the littoral 

 and lacustric zones, the highest percentage off Lorain, 

 Ohio. Its great abundance in the marginal zone indi- 

 cates that it breeds there during the spring or early 

 summer, and when it becomes sufficiently numerous 

 migrates out into the lake in small numbers. Such 

 migration is mostly confined to the littoral zone and 

 lasts only a short time, so that in September the spe- 

 cies is again confined to the marginal zone. It is 

 eaten by the Cisco and yellow perch. 



56. Eurycercus lamellatus (O. F. Milller). 

 Found in the marginal zone at 6 Canadian and 1 

 American stations; abundant only in the ponds on 

 Point Pelee where it was breeding. Eaten by carp 

 sucker and yellow perch. 



57. Graptoleberis testudinaria (Fischer). Re- 

 ported by Bigelow (1922) in small numbers in the 

 ponds on Point Pelee; not obtained during the present 

 survey. Not found in the stomach of any of the lake 

 fish. 



58. Holopedium gibberum Zaddach. Found in 

 very small numbers in the littoral and lacustric zones 

 during June and July, but disappearing entirely in 

 August and September. Since this cladoceran was 



not found anywhere in the marginal zone we have 

 to conclude either that it is pelagic and breeds in 

 the open water or that its breeding areas in the mar- 

 ginal zone were so exceptionally restricted as to 

 escape notice. Its presence in the tows of June and 

 July and disappearance later suggest that its breeding 

 period occurs earlier in the year. In June it was con- 

 fined to the middle of the lake but during July it ap- 

 peared also at the eastern end. It is eaten by the 

 Cisco. 



59. Ilyocryptus sordidus (Lieven). Found at 9 

 marginal zone stations at the eastern end of the lake 

 but divided subequaUy between the Canadian and 

 American shores, reported by Bigelow (1922) from 

 the ponds on Point Pelee but not obtained there dur- 

 ing the present survey. Often found in mud washings; 

 eaten by the carp. 



60. Ilyocryptus spinifer Herrick. Found at 6 of 

 the marginal stations in the middle and at the west- 

 ern end of the lake and on both shores. It is eaten 

 by carp and the carp sucker. 



61. Kurzia latissima (Kurz). Found only in the 

 ponds on Point Pelee and Lackawanna Pond in the 

 Hertel suburb of Buffalo. It is eaten by the yellow 

 perch and an unidentified minnow. 



62. Latona setifera (O. F. Milller). Found in 

 the ponds on Point Pelee, in Grand River at Fairport, 

 Ohio, and in Lackawanna Pond, Buffalo. Eleven 

 specimens were also taken in the Helgoland trawl in 

 the center of the eastern end of the lake, but none 

 appeared in any of the meter net hauls. This would 

 indicate that when it gets away from the marginal 

 zone into deeper water it sticks closely to the bottom. 

 Eaten by the carp sucker. 



63. Latonopsis occidentalis Birge. Reported by 

 Bigelow (1922) from the ponds of Point Pelee, but 

 obtained during the present survey only in the stom- 

 ach contents of small fish. Eaten by yeUow perch. 



64. Leptodora kindtli (Focke). Found at 14 

 of the marginal stations and in the other zones. A 

 large number were also washed out of flocculent de- 

 bris from Eighteen Mile Creek above its mouth and 

 at the mouth of Cattaraugus Creek. These were all 

 very small, only 2 or 3 mm. long, and were probably 

 hatched in the immediate vicinity since at their stage 



169 



