As part of a baseline study of chytridiomycete fungi in two Maine lakes, a polycentric, chitinophilic, and heretofore undescribed zoosporic fungus was found. The tubular thallus of Lacustromyces hiemalis gen. et sp.nov. has intercalary thin-walled zoosporangia, has thick-walled resistant sporangia, and does not grow at temperatures greater than 23 °C. Transmission electron microscopy revealed that its zoospores are a variant of the chytridialean type. The microbody – lipid globule complex is of a previously undescribed type, lacking a rumposome or other membrane cisterna and consisting of multiple lipid globules enclosed in a microbody that extends towards the kinetosome. Three kinds of microtubule roots arise near the kinetosome, a root leading to the microbody, a ribosomal root, and a microtubule organizing center that gives rise to microtubules that extend singly into the cytoplasm. Key words: Chytridiales, fungus, Lacustromyces, lake, ultrastructure, zoospore.