Euthemisto.

Euthemisto antarctica Dana and Euthemisto gaudichaudi Guérin.

A species of Themisto is frequently washed up on the shores of New Zealand, but the identification of it has given rise to a considerable amount of uncertainty and difference of opinion. In 1879 specimens were examined by Mr. G. M. Thomson, and by him were referred to Themisto antarctica Dana. He quoted the description given by Spence Bate in his Catalogue of the Amphipoda in the British Museum, and added a description of the female and of the young taken from the incubator pouch. In the “Challenger” Report Stebbing identified one of the species collected with that described by Thomson, but gave it the new name of Euthemisto thomsoni, being of opinion that it was different from Dana's species. In the “Challenger” Report he also recorded specimens of E. gaudichaudii Guérin, and figured this as well as the species which he called Euthemisto thomsoni. The chief character which induced Stebbing to consider the New Zealand specimens distinct from Dana's species was that the body is usually dorsally carinated in the adult animals, while this carination is not mentioned by Dana. In 1889, however, Bovallius pointed out that the development of the carina is a varying character in all the species that he had examined, and is usually less distinct in an ovigerous female than in a male of the same size. For this and for other reasons he concluded that Stebbing was not correct in his identifications, but that his E. gaudichaudii was really the same as E. antarctica Dana, while his E. thomsoni was identical with E. gaudichaudii Guérin.

I have examined specimens washed up at different times on various parts of New Zealand coast, and, while there is not much doubt that they are the same as those described by Stebbing under the name E. thomsoni, I have been unable to determine whether this should be referred to E. gaudichaudii, as Bovallius thinks, or to E. antarctica. Of these two “species” Bovallius (1889, p. 295) says, “They are closely allied, and less easily distinguished from one another than the two northern forms; the best distinguishing mark being, however, the relation between the length of the first and second pairs of uropoda.” I have been unable to distinguish my specimens into these two groups by this character, and the last manuscript note that I had made about them was that the two species appeared to be identical.

Shortly afterwards I received Dr. K. Stephensen's final report on the Hyperiidea of the Danish Oceanographical Expedition, 1908–10, to the Mediterranean and the adjacent seas. In this he uses the generic name Themisto to include Parathemisto Boeck and Euthemisto Bovallius, and unites the two northern species T. compressa Göes and T. bispinosa Boeck under the name of T. compressa. He gives elaborate descriptions and comparisons of different specimens obtained by the Danish expedition,