60 EXPEDITION ANTARCTIQUE BELGE 



end of the next, and within this tube is a considérable mass of parenchym, often forming 

 stout strands. At the end it is attached to the rosette plates, and there are also two latéral 

 connections to the neighbouring zocecia. There is a similar long tubular connection in 

 Tubucellaria opuntioides Pall., Poriua borealis Bush, a few other species, and in Cellaria generally. 

 In Porina borealis there are similar stout parenchym strands. There is a small denticle over 

 the distal rosette plate of B. denticulata. The zoœcia may be said to turn to the front and 

 to the two sides and not towards the back ; but in eut sections the base of the proximal 

 ends of the zoœcia are opposite, both laterally and dorsally. This may indicate that it is 

 derived from forms in which the zocecia were turned in ail directions, but this must remain 

 problematic. In other species called Bifaxaria bv Busk the zoœcia are only latéral. Bifaxaria 

 is however only retained provisionallv. 



Levinsen (') says that Bifaxaria denticulata B. is nearly related to Porina borealis B. 

 In conséquence I felt, that it was incumbent on me to see how far the northern Porina 

 borealis represented the southern Bifaxaria denticulata and M 1 Levinsen kindlv sent me some 

 spirit spécimens of P. borealis, for the purpose. However from a letter I hnd that Levinsen 

 had not intended to indicate, that the relationship was as close as I had understood him 

 to mean, and therefore no discussion of their geographical distribution is required. 



Whether the}- will ultimately be placed in the same familv, which is ail that M r Levinsen 

 expects, cannot be décidée!, until we know more upon what characters the families will 

 ultimately be based. 



In Porina borealis the zoœcia are arranged round an imaginary axis, there is a suboral 

 pore, the calcareous walls contain but verv little organic matter, there are pore tubes through 

 this shell wall, and in places thèse pore tubes are replaced by avicularia, which is unusual 

 in the Bryozoa. Thèse avicularia and those by the aperture hâve semicircular inaudibles. 



Habitat. — Challenger Station 320 (South Atlantic, Off the Argentine) 600 fathoms 

 (973 mètres). 



Exp. Antarct. Belge. 



X" 3og, Tangles II. Lat. 71 14' S.- Long. S9 14' W.; 460 met.; -to.3 C. 

 N« 33g, Tangles IV. Lat. 71° 18' S.- Long. 88» 02 W.; 435 met. ; — o.3 C. 

 N° 565, Tangles VIL Lat. 70° 23' S.- Long. 82° 47' W. ; 480 met.; +0.8 C. 

 One spécimen from 3og is attached to Retepora laevigata nov. 



Bifaxaria rustica (d'Orbigny) 



P). VIII, figs. 19a, b) 



Pustulopora rustica D'Orbigny, Voyage dans l'Amérique méridionale, p. 22, pi X, figs. i3-i5. 



Zoarium erect, slightly compressed, branching in one plane, zoœcia opening on the 

 anterior surface onby, attached at the base by chitinous radicles. The peristomial openings 

 are nearly round and the région of the aperture is somewhat raised ; the oral aperture however 

 has not been seen. The anterior and dorsal surfaces hâve long pores or pits, suggesting the 

 genus H oimera ; however sections showing the two or four opposite zoœcia prove at once, that 



(1) Levinsen, G. M. R., Studies on Bryozoa. (Vidensk. Medd. fra d. Naturh. Foren. i Kjôbenhavn, 1902, p. 26.) 



