I-iRYOZOA 75 



In 0. clavata the muscles are attached to the operculum in a pit, instead of to a projection 

 as is usually the case. 



Habitat. — Exp. Antarct. Belge. 



N os 343, 1047, Tangles IV. Lat. 71 18' S.- Long. 88° 02' W. ; 435 met.; — o.3 C. 

 N° 428, Tangles VI. Lat. 71° 19' S.- Long. 87 3y' W.; 436 met.; —0.2 C. 

 N° 6i5, Tangles VIII. Lat. 70 00' S.- Long. 8o° 48' W. ; 5oo ? met. ; +0.09 C. 



ORTHOPORA gen. nov. 



In the Ortkofiora compacta sp. nov. the lower edge of the oral aperture and of the oper- 

 culum is straight, and the muscular attachments are close to the distal edge of the operculum. 

 The ovicell is placed proximally to the oral aperture as in Turritigera stellata, and probably 

 in a few other species placed now under Cellepora, and on account of the position of the ovicell, 

 it has seemed necessary to form a new genus, but as only one species is known, much cannot 

 be said about it, nor can we be sure that it will be permanently retained. 



Orthopora compacta sp. nov. 



(PI. V, figs. 4«-«) 



This is allied to Turritigera, in having the ovicell situated proximally to the oral aperture, 

 which is the most distinguishing character of T. stellata B., although it was not appreciated 

 when first described, for the « tumid prominence » referred to by Busk is the ovicell. The 

 zoarium is erect, branching, cylindrical. The zoœcia are porcellanous, inflated ; and above 

 the oral aperture there is a long process bearing an avicularium, with a triangular mandible. 

 The calcareous tube leading from the avicularium is very distinctly seen when the avicularian 

 process is broken away. In many Cellepora: the avicularian tubes are in the wall of the zoœcia 

 or peristome, but hère they form a projection into the peristome, and the same structure 

 is seen in Turritigera stellata B. 



The operculum is straight below, and the muscular attachments are quite at the distal 

 end (fig. 46) so that from the position of the muscular attachments it could be distinguished 

 from ail other species, with which I am acquainted. There are occasionally on the surface 

 of the zoœcium one or two small triangular avicularia, also sometimes two similar ones on 

 the ovicell, and they may occur on the oral avicularian process. There are a few vicarious 

 avicularia with spatulate mandibles. Sections show a marked peculiarity in the tentacular 

 sheath, which in most species is quite thin, showing a few nuclei at intervais, as figured by 

 Calvet, Levinsen, and others but in 0. compacta it is three or four times the usual thickness, 

 and shows the darkly stained longitudinal muscular band. The parenchym, with nucleated cells 

 is found on each side of the sheath. The sheath of Cellepora bispinata B. is also very thick. 



There are 24 tentacles and no oral glands were found. In Lagenipora granum Hincks 

 there are 12 tentacles ; in Cellepora pumicosa B. i5-20 ; in C. caminata Waters 16 ; in C. sardonica 

 Waters i3 ; in C. verruculata Sm. 14 ; in C. incrassata Sm. 17 ; in C. ventricosa Lorenz 21 ; in 

 Osthimosa evexa Jull. there are 10 (fide Jullien) ; in Lagenipora Costazii Aud. 12 ; in Cellepora 

 bispinata B. there are 16; in Osthimosia clavata nov. 18; C. horneroides nov. 18-20. The O. compacta 

 is very similar to Cellepora solida Busk, and at first was thought to be identical, but upon 



