Cryptosporidium parvum (sp. nov.) a coccidium found in the small intestine of the common mouse.

Tyzzer described an even smaller species of cryptosporidium, Cryptosporidium parvum (sp. nov.), later recognized as the chief species infecting humans. His paper reproduced color lithographs of all the different life stages of the parasite.

(Thanks to Juan Weiss for this reference and its interpretation.)