. Echinoidea of the Swedish South Polar Expedition. Sea urchins. 92 TH. MORTENSEN, (Schwed. Sudpolar-Exp. answers, upon the whole, very well to the careful and accurate description given by KOEHLER; but, since Professor KOEHLER had likewise only a single specimen at his disposal, it is not surprising that I have some additional information to give. In PI. XI Figs. 17, 19 are given photographic representations of the specimen, which seem to me not superfluous, especially in view of the several minor differences from the type, as figured by KOEHLER. The shape of the test is as in the type specim
. Echinoidea of the Swedish South Polar Expedition. Sea urchins. 92 TH. MORTENSEN, (Schwed. Sudpolar-Exp. answers, upon the whole, very well to the careful and accurate description given by KOEHLER; but, since Professor KOEHLER had likewise only a single specimen at his disposal, it is not surprising that I have some additional information to give. In PI. XI Figs. 17, 19 are given photographic representations of the specimen, which seem to me not superfluous, especially in view of the several minor differences from the type, as figured by KOEHLER. The shape of the test is as in the type specimen, excepting that it is somewhat lower (length 48 mm., breadth 43 mm., height 29 mm.). The vertex is central. The apical system differs rather much from that of the type specimen, as figured by KOEHLER (Op. cit. PI. VI Fig. 43). Only three genital pores are developed, the right anterior one is wanting, while it is developed in the type specimen. In the figure quoted the madreporic plate is represented as being separated from the right anterior genital plate by a transverse line; in the text nothing is said of this very unusual feature, which — as it cannot be supposed to be an error in the figure, it being expressly stated that the plates of the apical system are very distinct — I would sug- gest to be an abnormality. In any case the present specimen shows the usual condition, the madreporic plate being the posterior prolongation of the right anterior genital plate (Fig. 24). — The fact that such a case is also met with in Amphipn. Koelderi (comp. below, p. 98 Fig. 28) should be mentioned on this occasion; there it is evidently an abnormality. The ambulacra correspond to those of the type specimen, the number of the plates only being slightly smaller, in accordance with the smaller size of the specimen. Regarding the inter- ambulacra it should be noticed that the plates are not elevated in the middle, as is the case in the type specimen. In the structure of the actinal p
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1910
