Echinoidea of the Swedish South Echinoidea of the Swedish South Polar Expedition echinoideaofswed00mort Year: 1910 96 TH. MORTENSEN, (Schwed. Sudpolar-Exp. actinal side the primary tubercles are somewhat larger. The labrum is very pro- minent; it reaches backwards to the middle of the second ambulacral plate; in one specimen (male), however, the first adjoining ambulacral plate of ambulacrum I is very elongate, and the labrum does not reach beyond it. In this specimen the right sternal plate is the largest, the suture between the two sternal plates continuing into the suture between the first
Echinoidea of the Swedish South Echinoidea of the Swedish South Polar Expedition echinoideaofswed00mort Year: 1910 96 TH. MORTENSEN, (Schwed. Sudpolar-Exp. actinal side the primary tubercles are somewhat larger. The labrum is very pro- minent; it reaches backwards to the middle of the second ambulacral plate; in one specimen (male), however, the first adjoining ambulacral plate of ambulacrum I is very elongate, and the labrum does not reach beyond it. In this specimen the right sternal plate is the largest, the suture between the two sternal plates continuing into the suture between the first and second plate of the inner series of the left ambu- lacrum (I). The plastron is rather narrow, though less so than in A. Lorioli; the suture between the two sternal plates is distinct. The apical system (Figs. 26—27) is like that of A. Lorioli (the specimen in this collection); the madreporic plate separates the posterior genital and ocular plates, but does not reach beyond the posterior ocular plates. Only three genital pores are developed, the right anterior one is wanting; they are small in the male, rather large in the female. Fig. 26. Fig. 27. Figs. 26—27. Apical system of Amphipn, Koehleri, male (26) and female (27). A most conspicuous difference from A. Lorioli is found in the position of the periproct; it is placed on the posterior, vertical end of the test, so that it cannot be seen from the actinal side; it is more or less sunken. It is somewhat variable as to size and form, but, upon the whole, it may be said to be a little elongated, pointed in one or both ends; it is covered by small plates in the usual way. The peristomial region is somewhat sunken; the first interambulacral plates not excluded from the peristome, which latteris of the usual size. The plates of the peri- stome are covered with miliary tubercles carrying pedicellarise. The spines are rather long and coarse, of uniform length, covering the petals and the apical system completely; those of
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