Briefly described by van Beneden (1858) as Crepina gracilis, Phoronis gracilis has been collected by Selys-Longchamps (1903) in Helgoland. The descriptions do not allow to distinguish this species from Phoronis hippocrepia. Thus, Silén (1952) proposed the synonymy of both species, that has been suggested previously by Wright (1859).

To know more about this synonymy, please read the papers which are cited below.

References

Beneden P. van, 1858. Note sur un annélide céphalobranche sans soies, désigné sous le nom de Crepina. Ann. Sci. nat., 10, 11-23 et Bull. Acad. Roy. Sci. Belgique, (2) 5, 450-465.

Emig C. C., 1971. Taxonomie et systématique des Phoronidiens. Bull. Mus. Nat. Hist. nat. Paris, (Zool.) 8, 469-568.

Selys-Longchamps M. de, 1903. Über Phoronis und Actinotrocha bei Helgoland. Wiss. Meeresunters., Helgoland, 6, 1-55.

Selys-Longchamps M. de, 1907. Phoronis. Fauna Flora Neapel, 30, 1-280.

Silén L., 1952. Researches on Phoronida of the Gullmar Fiord area (West coast of Sweden). Ark. Zool., 4 (4), 95-140.

Wright T. S., 1859. Note sur la Crepina de van Beneden. Ann. Sci. nat. (Zool.), 11, p. 150.

Cori (1989) named Phoronis caespitosa specimens he referred a year later to P. kowalevskii.

To know more about this synonymy, please read the papers which are cited below.

References

Cori C. J., 1889. Beitrag zur Anatomie der Phoronis. Inaug.-Diss. Prague (Univ. Leipzig), 48 pp.

Cori C. J., 1890. Untersuchung über die Anatomie und Histologie der Gattung Phoronis. Z. wiss. Zool., 51, 480-568.

Phoronis kowalesvkii has been discovered by Kowalevsky (1867), described by Caldwell (1882) and finally named by Benham (1889). Selys-Longchamps (1907) demonstrated, in his monography, that this species is a variety of P. hippocrepia.

To know more about this synonymy, please read the papers which are cited below.

References

Benham W. B., 1889. The anatomy of Phoronis australis. Q. J. microsc. Sci., 30, 125-158.

Caldwell W. H., 1882. Preliminary note on the structure, development and affinities of Phoronis. Proc. Roy. Soc. London, 34, 371-383.

Emig C. C., 1971. Taxonomie et systématique des Phoronidiens. Bull. Mus. Nat. Hist. nat. Paris, (Zool.) 8, 469-568.

Kowalevsky A., 1867. Anatomy and development of Phoronis (in Russian). [Analysis in Leuckart, 1867] Thesis St-Petersburg,

Selys-Longchamps M. de, 1907. Phoronis. Fauna Flora Neapel, 30, 1-280.

Phoronis capensis , owing the succinct description of Gilchrist (1907), appears as a synonym of P. hippocrepia (see Emig, 1971). Gilchrist himself wrote : "P. capensis, closely related to Ph. hippocrepia."

To know more about this synonymy, please read the papers which are cited below.

References

Emig C. C., 1971. Taxonomie et systématique des Phoronidiens. Bull. Mus. Nat. Hist. nat. Paris, (Zool.) 8, 469-568.

Gilchrist J. D., 1907. New forms of the Hemichordates from South Africa. Trans. S Afr. Phil. Soc., 17, 151-176.