55 EXPÉDITION ANTARCTIQUE BELGE 



Systenopora contracta sp. nov. 



(PI. V, figs. K7-/;) 



The zoœcia do not show external marks of séparation, the surface has large pits, and 

 the région of the peristomial aperture is raised. The secondary aperture is slit-like in the 

 direction of the zoarial axis, being formed by a plate, which slopes diagonally inwards on 

 the one side, and terminâtes with a straight edge ; on the other side there is an ear-like 

 projection, at the base of which there is a circulai' avicularium, with beaked nearly semi- 

 circular mandibles. There are two or three other circulai- avicularia situated near the aperture, 

 and further there is (') within the aperture (but quite invisible until sections hâve been 

 made) a fairly large avicularium (figs. ik, l) with a triangular mandible, having a central 

 lucida, and resembling the semicircular mandibles to the external avicularia. This is entirely 

 under the diagonal plate. The oral aperture is some distance from the slit-like secondary 

 aperture and is transverse to the zoarial axis (fig. ig); it is nearly round, but slightly flattened 

 on the top, namely the edge nearest to the zoarial border. There does not secm to be any 

 chitinous operculum, but a strong bundle ot muscles appears to draw the lining membrane 

 over the aperture. 



The ovicells are entirely concealed, though where the ovicells occur there is over part 

 of the wall an absence of pits. There are, as a rule, six latéral rosette plates, having 

 several communication pores; and on the distal walls numerous communication pores extend 

 over an irregular area, which is really the rosette plate. Above this rosette plate we find 

 a pair of stout cervicorne processes, irregularly curving over the communication pores, and 

 growing from each side (figs. ig, h, i). Thèse are probably homologous with the comb-like 

 process, which I described as occurring in Membranipora tehuelcha (d'Orb.) ( 2 ) and in Membranipora 

 nitens Hincks, though in both cases the comb-like process is some distance from the base 

 of the zoarium. To thèse I also refer when describing an internai denticle in Scntpocellana 

 antarctica sp. nov. 



There are about 20 tentacles. 



The zoarium is grey and the zocecia are loaded with pigments and foreign matter, 

 which has made the examination difficult. There are no complète polypides in the sections 

 eut (612), but there are many brown bodies, and also embryos in a growing condition, 

 as well as testes. The muscles of the compensation sac start from the lower wall as isolated 

 threads, but on the upper wall several are attached close together. 



Habitat. — Exp. Antarct. Belge. 



N cs 612 (12 pièces), 621 (1 pièce), 623 (1 pièce), 683 (10 pièces), 991 (fragments), 

 Tangles VIII. Lat. 70" 00' S.- Long. 8o° 48' W. ; 5oo? met.; +0.9 C. 



(1) Levinsen, G. M. R., Studies on Bryozoa {Vidensh. Medd. fra d. Naturh. Forai, i Kjobcnhavn, 1902, p. 21), 

 speaks of an internai avicularium in Flabdlaris roborata (Hincks), but the avicularium in that case is of the Membrani- 

 pora Flemingii type, and although not readily seen, as it is far within the area, yet it is scarcely internai like that 

 of S. contracta. Perhaps the avicularium of Schizoporella challengeria Waters should be compared with the internai 

 avicularium of 5. contracta. 



(2) Waters, On Membraniporidae. [Journ. of the Linn. Soc. Zool., vol. XXVI, p. 675.1 



