The descriptions of two new planktonic rotifers, both cold stenotherms, is presented. Notholoca laurentiae n. sp. is a predominant winter rotifer of the Laurentian Great Lakes, but to date has not been found in inland lakes of the region. Morphologically its closest relative is the European brackish water species, N. salina Focke. Notholca michiganensis n. sp. has been recorded only in the oligotrophic inland lakes of the northern portion of Michigan’s lower peninsula during winter and early spring (water temperatures 0.5-5.2C). Morphologically, N. michiganensis is similar to, but distinctly smaller than N. frigida Jaschnov.