EXPÉDITION ANTARCTIQUE BELGE 



aperture, continued in the distal part to a rostral process carrying an avicularium with small 

 triano-ular mandibles. On the front of the zoœcium, below the aperture, there is a small 

 semicircular avicularian chamber, round which there are large pores irregularly placed, and 

 a few semicircular avicularia are irregularly situated on the zoœcia. There is also a large 

 vicarious avicularium with broadly spatulate mandible. Ovicells unknown. Only small frag- 

 ments were found, so that no dissections hâve been possible. I should not hâve ventured 

 to place it under 0. signata from Busk's figures, but an examination of the Challenger 

 spécimens show that both O. signata B. and C. canaliculata B. hâve the winged-like process on 

 the peristome. The spécimen is however too small to speak with absolute certainty as to its 

 position. It apparently belongs to the Osthimosia eatonensis group, but the zoœcia are very 

 much larger, and it is also closely related to Cellepora canaliculata Busk. 



Habitat. — Challenger Station, 304 (Patagonia). Lat. 46 53' S.- Long. 75° 11' W. ; 

 45 fathoms (73 mètres). 



Exp. Antarct. Belge. 



N° 991, Tangles VIII. Lat. 7o°oo' S.- Long. 80048' W. ; 5oo ? met. ; +0.9 C. 



Osthimosa clavata sp. nov. 



PL VII, figs. m 



Zoarium erect, forming thick cylindrical branches, the lower part of which is dark, while 

 the ends are clear, white, porcellanous ; the extremities are clavate. The zoœcia are globular, 

 imperforate, smooth, bearing an avicularium on a rostrum at the distal end of the aperture, 

 and there are a few small round avicularia scattered about, also some vicarious avicularia 

 with verv short thin spatulate mandibles. The operculum is about o.i2 mm wide with the 

 muscular attachments o.o5 mm apart. The ovicells are not very distinct, as the}- are merely a 

 greater inflation of the distal portion of the zoœcium, however where a view into the ovicell is 

 obtained, it is seen to be widely open and it cannot be closed by the operculum ; there is a 

 wide area to some ovicells but not to ail. 



The number of tentacles is 18, and there are ova and testes with spermatozoa in the 

 zoœcia, but no oral glands are found. The ovaria are often much compressed, having one or 

 two cells with large nuclei. 



This is very much like the Osthimosia (Cellepora) eatonensis Busk ('), but the two are 

 considered to be distinct, for the growth of this Antarctic form is peculiar, and the short 

 vicarious avicularium differs from the long one of O. eatonensis B. with its thick mandible. 



A small spécimen from N° 6i5, which I think is this species, lias the semicircular avicu- 

 laria more abundant, especially round the aperture. This is a young growth on stone and 

 is porcellanous. 



(1) Osthimosia eatonensis Busk was subsequently described by Jullien as Osthimosia evexa Jull. In Busk's 

 description of the Challenger O. eatonensis he does not mention the ovicells, but they occur from Station 149 D. 

 being widely open with a flattened area ; from St. 3i5 they are widely open, imperforate, with a Une but the area is 

 not very distinct ; from 3o3 (which Sir John Murray thinks ma}- be 3o8) there are similar globose ovicells. 



