W. E.  Ritter, ?The structure and affinities of Herdmania claviformis, the type of a new genus and family of ascidians?, Mark Anniversary Volume, vol. 12, pp. 235-261, 1903.

W. E.  Ritter, ?Papers from the Harriman Alaska Expedition. XXIII. The Ascidians?, Proceedings of the Washington Academy of Sciences, vol. 3, pp. 225-266, 1901.

W. E.  Ritter, ?Some ascidians from Puget Sound. Collections of 1896?, Annals. New York Academy of Science, vol. 12, pp. 589-616, 1900.

W. E.  Ritter, ?Notes on the structure and development of the type of a new family of so-called social ascidians from the coast of California?, Science, new series, vol. 5, pp. 434-435, 1896.

W. E.  Ritter, ?Tunicata of the Pacific coast of North America?, Proceedings of the California Academy of Sciences, series 2, vol. 4, pp. 37-80, 1893.

W. E.  Ritter and Forsyth, R. A., ?Ascidians of the littoral zone of southern California?, University of California Publications in Zoology, vol. 16 (24), pp. 439-512, 1917.

W. E.  Ritter, ?The simple ascidians from the north-eastern Pacific in the collection of the United States National Museum?, Proceedings of the United States National Museum, vol. 45, pp. 427-505, 1913.

W. E.  Ritter, ?The ascidians collected by the United States Fisheries Bureau Steamer Albatross on the coast of California during the Summer of 1904?, University of California Publications in Zoology, vol. 4(1), pp. 1-52, 1907.