184 THE PELAGIC NUDIBRANCH, CEPHALOPYGE TREMATOIDES (CHUN, 1889), IN NEW SOUTH WALES WITH A NOTE ON OTHER SPECIES IN THIS GENUS. By Joan E. Steinberg, Fulbright Scholar, Department of Zoology, University of Sydney. (Plate xi; eight Text-figures.) [Read 29th August, 1956.] Synopsis. The Phyllirhoid nudibranch, Cephalopyge trematoides (Chun, 1889), is recorded from Port Jackson, N.S.W. On the basis of variations observed in Australian specimens, the validity of the six species in Cephalopyge is discussed and it is concluded that they all should be synonymized with C. trematoides. The specimens from New South Wales are described. In 1936 Dakin and Colefax published a description of a pelagic nudibranch belonging to the family Phyllirhoidae from five specimens taken off the coast of New South Wales which they referred to the genus Ctilopsis Andre, 1906. A year later, on the basis of further investigation of the literature, they reassigned their specimens to the genus Cephalopyge Hanel, 1905, with which Ctilopsis had been synonymized (Thiele, 1931) and stated, moreover, that they appeared to be a southern variety of C. orientalis Baba, 1933. On the morning of October 27, 1955, many Cephalopyge were observed swimming near the end of a small wharf in Camp Cove just inside Inner South Head, Port Jackson, N.S.W. Also present were large numbers of small salps. Approximately one hundred Cephalopyge were collected on this and the following day. They appeared to be less abundant on the 28th. The animals were observed and photographed alive and motion pictures were taken of their swimming movements. Some were relaxed with menthol and others were killed without relaxation with dilute glacial acetic acid. All were preserved in alcohol. They were identified as Cephalopyge trematoides (Chun, 1889). One specimen of Cephalopyge collected by Dakin and Colefax and two specimens of ■Cephalopyge trematoides collected off the coasts of Southern and Lower California (see Dales, 1953) have been examined by me and compared with my specimens. In all there have been six species included in the genus Cephalopyge. These are based on eleven collections, totalling few more than thirty specimens, with no collection containing more than about five. To my knowledge only one has ever been seen alive (Pierantoni, 1923). Odhner, in his revision of the Dendronotacea (1936), lists five of the species: C. trematoides (Chun, 1889), C. mediterranea (Pierantoni, 1923), C. orientalis Baba, 1933, C. picteti (Andre, 1906) and C. michaelsarsi (Bonnevie, 1921). The sixth, C. arabica Stubbings, was described in 1937. The genus had been divided into two subgenera by Thiele (1931) on the basis of the development of the foot, but Dakin and Colefax (1937) questioned the validity of this division and the variation in my specimens shows that this character is, as they suggested, dependent on the amount of contraction or expansion at the time of preservation. The use of the number of hermaphrodite glands in separating species was also thought by these authors and by Stubbings (1937) to be unsatisfactory. Dakin and Colefax found it necessary to make a careful examination of serial sections in order to determine the number of glands and so questioned the findings of previous authors in regard to the number they had recorded. Stubbings felt that the actual number was



The pelagic nudibranch, Cephalopyge trematoides (Chun, 1889), in New South Wales with a note on other species in this genus

J E Steinberg
Proceedings of The Linnean Society of New South Wales 81: 184-192 (1956)

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