the Trondhjem Fiord. 447 
which marks its separation from the mouth-margin; the 
illusion is heightened by the fact that the anterior edge of the 
operculum is projected at a right angle across the mouth, 
ieaving in front an opening exactly semicircular in form. 
The whole cell thus mimics the appearance of a Lepralian. 
Two avicularia on each cell—one ceutral, raised, situated a 
little behind the aperture; the other lateral, in the usual 
position, very small, the outer margin of the cell embracing 
it from below without any angularity. The ocecium is rather 
longer than wide, not globose, but depressed slightly above, 
inclining inwards. 
But a most marked peculiarity of this Mentpea is seen at 
the back of the zoarium, which is overlaid throughout from 
the base to the most recently developed cells by chitinous 
tubes; these tubes, where not so numerous, generally wind 
in and out among the cells, but on the lower part, where they 
are more numerous, they completely cover the whole back ; 
moreover, one of these tubes generally (if not always) passes 
round the base of each bifurcation (see Quart. Journ. tig. 6, and 
here, Pl. XIX. tig. 1, c), as though to give strength to that part ; 
sometimes also one of the tubes runs along the edge of each 
side of the zoarium, so that, when viewed from above, there 
is seen a transparent margin (Pl. XIX. fig. 1, 6) extended 
outside the cells. Height of my tallest specimen 32 millim. 
(not quite 14 inch). 
Rédberg, Trondhjem Fiord, 150 fath.; also Kors Fiord, 
180 fath. ; Hardanger Fiord, 150-180 fath.; Floré, 35 fath. ; 
and Bog Fiord, Kast Finmark, 150 fath. 
Specimens from all these localities agree in every particular. 
They are at once distinguished from all other species of the 
genus by the peculiar dorsal overlying of chitinous tubes and 
the large close-fitting cap-formed fornix, as well as by the 
presence of the central and the small size of the lateral 
avicularia. 
The description and figure here of this species are so 
different from those previously given that some explanation 
is necessary. Alder’s figure illustrating my paper (pl. v. 
fig. 8) and Hincks’s figure (pl. ix. tig. 1) were both taken from 
the same specimen ; the former incorrectly thought that the 
broken remains on the upper ocecium-bearing cell repre- 
sented a branched fornix. This error I corrected in my 
description, and Hincks drew it as entire, adding two similar 
fornices to two other cells where they were not actually 
present in the specimen. I mention this trifle because 
the curious circumstance is this, that all the time there 
was a perfect fornix on the lowest zocecium otf the right-hand 
