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THE VOYAGE OF H.M.S. CHALLENGER. 
however, that the peculiar conformation of the operculum, and other chitinous parts, will 
be found characteristic in what might be termed the whole moniliferous group. 
(13) Retepora mucronata , n. sp. (PI. XXVI. fig. 6). 
Character. — Zoarium probably much folded and irregularly contorted. Fenestrse 
broad, oval, about 0"‘02 long, tolerably uniform. Zooecia subrhomboidal in out- 
line, completely immersed ; anterior wall very thick, smooth and porcellanous ; 
dorsal surface finely granular, with very distinct vibices and numerous small 
scattered immersed avicularia. Orifice orbicular. Peristome not raised, thickish, 
with a very minute labial sublateral fissure and pore ; the lower or anterior lip 
on one side, often projecting into a pyramidal mucro or spout (fig. 6c). Ocecia 
subimmersed, depressed, with a small pore near the summit in front of a large trifoliate 
perforated stigma (fig. 6d). Anterior avicularia very rare, with a long spear-shaped 
mandible (fig. 6e), or sometimes with a blunt nearly semicircular one, like those on the 
dorsal surface. 
Habitat. — Station 208, lat. 11° 37' N., long. 123° 31' E., 18 fathoms, blue mud. 
A striking characteristic of this species is the peculiar translucent, thick, porcellanous 
nature of the zooecial wall, and the production of the peristome in the older cells into a 
strong short mucro (in the younger it more usually assumes the form of a short spout), 
and the very minute labial fissure and pore, which in fact are only visible in the youngest 
zooecia. 
It is represented in the collection only by two or three small dead fragments, so that 
the general habit and chitinous parts cannot be determined. 
(14) Retepora cuntortuplicata, n. sp. (PI. XXVI. fig. 2). 
Character. — Zoarium foliaceous, much and intricately folded, the folds frequently 
anastomosing (fig. 2a). Fenestrse oval, elongated, about 0"'02 long, 
very uniform. Zooecia wholly immersed, those in the middle of the 
branches flattened or concave in front. Surface smooth, entire, bordered 
by an acute raised septal line. Dorsal surface smooth, with well-marked 
but thin vibices. Orifice orbicular. Peristome rather thick, with a 
sublateral fissure, shortly terminating in a suboral pore ; a single oral 
spine on either side. Ocecia small, conical, acuminate, with a narrow 
trifoliate stigma. Anterior avicularia rare, placed on a small tubercular 
elevation, rather to one side of the front, close to the suboral pore. Mandible triangular, 
Fig. 30 . — Retepora 
contortuplicata. 
