Echinoidea of the Swedish South Polar Expedition echinoideaofswed00mort Year: 1910 TH. MORTENSEN, (Schwed. Siidpolar-Exp. there is at the lower edge of each plate a much smaller tubercle, the whole area thus carrying' four vertical series of tubercles. According to AGASSIZ (Revision of Echini p. 396) there are, besides the primary series, »two irregular vertical rows on each side of the median furrow, with a few miliaries scattered irregularly between the secondary tubercles towards the poriferous zone». Even in the largest specimens examined by me (26 mm. in diameter) I find only one second
Echinoidea of the Swedish South Polar Expedition echinoideaofswed00mort Year: 1910 TH. MORTENSEN, (Schwed. Siidpolar-Exp. there is at the lower edge of each plate a much smaller tubercle, the whole area thus carrying' four vertical series of tubercles. According to AGASSIZ (Revision of Echini p. 396) there are, besides the primary series, »two irregular vertical rows on each side of the median furrow, with a few miliaries scattered irregularly between the secondary tubercles towards the poriferous zone». Even in the largest specimens examined by me (26 mm. in diameter) I find only one secondary tubercle on each plate; the second of these small tubercles is thus evidently found only in still larger specimens (comp. below, the specimens from Altata?). — The median furrow is nar- row, but mostly quite distinct. The pores are described in the »Revision» as sad- joining; ridge separating pairs of pores prominent*. This is quite correct, and it need only be added that there is a distinct depression all round each pair (Fig. 4). (The difference in the shape of the pores between this species and E. mitrix has been emphasized in the Report on the Echinoidea of the German Southpolar-Expe- The apical system (PI. IV Figs. 5—6, 9—10; PI. XIV Fig. 6) is comparatively small, ca. 41—44 of the horizontal diameter of the test. The ocular plates are in larger specimens generally all in broad contact with the anal system. DODERLEINS statement (loc. cit.) that he finds »bei einem ziemlich grossen Exemplar ... das Analfeld vollstandig eingeschlossen von den Genitalplatten», evidently refers to the specimen of E. nutrix and thus has no bearing on any variability in this character in canaliculata. Further, when AGASSIZ says in ^Revision of Echini* p. 396: »Genital plates in contacb, which cannot mean anything but that the oculars are excluded from the anal area, I would suggest that »genitab is a lapsus calami for »ocular». — The ocular plates are distinctly broader
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