16 ARKIV FÖR ZOOLOGI. BAND 14. N:0 18. 



of which arise from a longitudnal band on either side of the 

 middle line». Leptoteredra has the dorsal surface )>toute 

 maculée de taches pigmentaires d'un jaune rougeåtre, excepté 

 sur ses bords et dans la region pharyngienne». It ought to 

 be recalled that both descriptions are made from preserved 

 specimens. 



Whether these differences Lave such a value that we 

 must distinguish between the specimens from Orkney Islands 

 and Graham Land as different species is not easy to make 

 out from the descriptions alone. It must be deplored that 

 no habitus figures are given for A. stylosiomoides. Anyhow it 

 is certain that they belong to the same genus, Leptoteredra, 

 and future investigations will perhaps reveal that there is 

 only one antarctic species in that genus. 



In speaking of Leptoteredra, interpreted at first as an 

 Aceros, I will make reference to another polyclad which I 

 think has been wrongly included in that genus. In a paper 

 published by H. Heath and E. A. McGregor (1912) an Aceros 

 langi n. sp. is described, in which no prostatic vesicle was 

 distinguished. If such a vesicle really is lacking it is im- 

 possible to regard that species as an Aceros. No »uterus 

 glands» (uterine vesicles) could be detected. It is not men- 

 tioned that the penis is armed and the schematic figiire is 

 too poor to allow of a statement in that respect. Further, 

 it is quite uncertain if marginal tentacles are absent or not. 

 The great number of cerebral eyes at least do not speak in 

 favour for the interpretation of it as an Aceros. As the 

 sexual organs do not agree with the type of the Pseudoceridw 

 and the Euryleptidce and as these organs are insufficiently 

 known, no sections having been studied, it is impossible to 

 discuss its relationship, all the more so as the anterior end 

 of the animal was also damaged. It must at present be 

 excluded from the genus Aceros. 



Curiously enough, Hallez in his låter memoir (1913) 

 knows nothing of the paper of the Scottish National An- 

 tarctic Expedition treating Antarctic polyclads, published 

 already in 1907. As I have pointed out (Bock, 1913) Nvchen^ 

 ceros orcadensis Gemmill & Leiper is identical with Stylochoi- 



