ALDER, ON NEW BRITISH POLYZOA. 97 
broader as it ascends, branching dichotomously, and tapering 
toa blunt apex. The ovicells are larger and more numerous 
than in the last species, and are distinctly perforated. Besides 
the avicularium on one side of the rostrum, there are small, 
circular avicularia scattered over the surface and between the 
cells, with a few larger spatulate ones interspersed. The 
specimens got by Mr. Hincks appear to have been of small 
size; but on the coast of Northumberland, where the species 
is not uncommon, it grows rather larger, though seldom 
reaching above an inch in height. It varies a good deal in 
form, sometimes spreading in a palmate manner, like an elk’s 
horn (fig. 3), sometimes consisting of more slender cylindri- 
cal branches of nearly equal thickness throughout (fig. 2). 
The typical form, however, is a little ventricose in the centre, 
and not much branched. 
CELLEPORA ATTENUATA, n. sp. (Pl. II, fig. 5—8.) 
Polyzoary very slender, white, cylindrical, nearly smooth 
below, a little roughened above, dichotomously branched, the 
branches of equal thickness throughout, and diverging on all 
sides. Cells immersed or very slightly raised, excepting 
those towards the extremities of the branches, which are a 
little more prominent; their surface is smooth, with small 
tubular perforations round the margins, and a few circular 
and slightly raised avicularia on the surface of the cells. 
Apertures nearly circular, with a slightly projecting rostrum 
below, bearing a small avicularium on one side; the rostra 
are obliterated in the lower portion of the stem and branches. 
Ovicells free, semicircular, decumbent, a little perforated. 
Height, about aninch; lateral expansion, rather less ; breadth 
of stem, =!;th of an inch. 
The species has yet only been found in Shetland, where it 
was first got by Mr. Barlee, in 1858. It has lately been ob- 
tained in the same locality, by the Rev. A. M. Norman. 
C. attenuata comes rather near to some varieties of the last, 
from which it may be known by its more slender form and 
uniform thickness throughout, by its smoother and more even 
surface, and likewise by the absence of the numerous avicu- 
laria of that species. Young individuals of this and the two 
preceding species are, with difficulty, distinguished from each 
other. In its typical form this species is very slender, and 
the cells are placed rather more regularly than is usual in 
the genus Cellepora, but occasionally a cell may be found 
reversed, or placed diagonally. 
