S + EXPEDITION ANTARCTIQUE BELGE 



Retepora gelida sp. nov. 



(PL VI, figs. ja-d) 



Zoaria with fairly large meshes, having the branches as a rule wider than the fenestrae, 

 though they vaiy much in width ; there are large fenestral avicularia with triangular mandibles. 

 The shape of the zoarium is unknown. The zoœcia are rhomboidal, distinct, separated by 

 raised lines, faintly granular, with a large, scarcely raised, avicularium directed transversely or 

 downwards, having a thin characteristic mandible which has a small lucida close to the 

 proximal end. The peristome is not much elevated, and has the border is most cases irregu- 

 larly serrate or nodulated, and sometimes, but not generallv, the peristome is raised at the 

 distal end. The operculum is short with the sides straight, the proximal border also straight 

 and the latéral borders are thick. 



The ovicell is subimmersed and has an irregular mark on the front, the wall being 

 thinner hère, and occasionally on this there is a broad Une with the wall still thinner, but 

 there does not seem to be a fissure. 



The dorsal surface is divided by vibices and there are elliptical avicularia. 



Habitat. — Exp. Antarct. Belge. 



\" 683, Tangles VIII. Lat. 70 00' S.- Long. 8o° 48' W.; 5oo?met. ; -f-c.9 C. 



Retepora hippocrepis sp. nov. 



(PL VI, figs. loa-g and figure in text) 



Zoarium very irregularly cup-shaped, with a solid base. The largest spécimen is very 

 unequal in the axes, the longest axis being about 70™", and the shortest about 20 mm , and the 

 growth cannot be said to be wavy or undulating. The fenestrae are fairly large, averaging 

 about 2 mm X o.6 mm and the branches are about as wide as the fenestrae. Fenestral avicularia 

 occur to nearly ail the fenestrae. 



The zoœcia are not always distinctly indicated, but there are raised dividing lines to 

 most of the younger zoœcia, the shape is elongate, oval, surface smooth ; below the aperture 

 is a long, stout, solid, calcareous, spinous process, thèse do not usually support an avicularium, 

 but in one or two cases there is a minute semicircular one directed towards the oral aperture, 

 and occasionally on the other side of the spine, there may be growing by it and partially 

 attached to it, a large raised avicularium with triangular mandible. On the surface of the 

 zoœcium in various positions, there are the tumid avicularian chambers of a small avicula- 

 rium, with semicircular mandibles, and besides thèse there are a few triangular avicularia, 

 similar to the fenestral avicularia, usually placed transversely or diagonally directed upwards. 



The oral aperture is nearly straight below, and contracted on each side towards the 

 lower part, while the condyles in the aperture are smaller than those of R. antarctica nov. The 

 ovicells are globular, much raised and fairly widely open below, never closed by the operculum, 

 nor does the operculum usually close the ovicells in Retepora ; on the front of the ovicell there 

 is the mark of a thinner part, either semicircular or more contracted, and often in the middle 

 is a wide line, which however does not seem to be a fissure. The dorsal surface is divided 



