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 plastron I find some 

 noteworthy differences from what is seen in the type specimen, as represented by 

 KOEHLER (Op. cit. PL V Fig. 37). The labrum is there shown to reach the fourth 

 ambulacral plate, and the sternum is undivided, the plastron thus being merido- 

 sternous. In the specimen before me the labrum ends off the third ambulacral plate, 

 and only the second ambulacral plate is quite short (Fig. 25), while in the type spe- 

 cimen the 3 — 4 inner ambulacral plates are represented as being quite short. The 

 sternum consists of two plates, after the usual amphisternous type (Fig. 25); the suture 

 between these two plates is, however, difficult to trace, and can only be seen with 

 certainty after treating the specimen with alcohol-glycerin. I cannot doubt that this 

 suture is really present also in the type specimen; a variation from the amphisternous 

 to the meridosternous type, even in one and the same species, is, I think, impossible. 



Fig. 24. Apical system of Amphi- 

 fncitstes Lorioli; the tubercles are 



