364 Rey. T. Hincks on the Genus Retepora. 
glossy granules. Round the upper part of the orifice they 
are frequently of larger size, and are ranged in line and placed 
close together, so as to have much the appearance of rudi- 
mentary spines. 
The oocecium in R&. granulata is described as ‘“ immersed 
and granular ;” in my specimens it is closely united to the 
cells about it, and the base may be slightly immersed, but 
its striking characteristics are its massiveness and prominence. 
It stands out boldly from the surface of the cell, sometimes 
smooth, sometimes much roughened and bearing several of the 
small avicularia. ‘The minute characters of the zoocecium and 
its orifice are not included in Macgillivray’s diagnosis. In most 
of the cells of the form which I have in view an oval avicula- 
rium, set transversely, occurs immediately under the lower mar- 
gin of the orifice, placed towards one side. Sometimes a second 
is present. Great numbers of similar avicularia are distributed 
over the cells, whilst the aviculiferous mamille, very dif- 
ferent from the tall acuminate processes which occur on other 
species, thickly stud the surface of the zoarium. The inoscu- 
lating branches are very thick and massive, and the meshes 
small and often suborbicular in shape. 
Macgillivray describes the zoarium of his 2. granulata as 
“expanded, foliaceous, convoluted.”” The habit of growth, 
as I have already remarked, has no specific significance in 
this tribe; but the fragments of the present species which 
I have examined show it to be caliculate and occasionally 
to form subcylindrical cavities. 
é 
4, Retepora cellulosa, Smitt *. 
This species has a wide range. It occurs in the Arctic seas 
and in the Mediterranean, but has not been obtained, so far 
as I know, on our own coasts. Darwin took it off Cape 
Horn Macgillivray, a slender variety of it, in Australia ; 
Hutton records it from New Zealand. I have a characteristic 
specimen from South Australia. 
EXPLANATION OF THE PLATES. 
PLATE XVIII. 
Fig. 1. Retepora Couchii, Hincks: natural size. 
Fig. 2. The same. 
Fig. 3. A portion of the zoarium, front surface, magnified. 
Fig. 4. A portion of the zoarium, dorsal surface, magnified. 
Fig. 5. A single zoocecium, magnified. 
Fig. 6. One of the larger avicularia. 

* Kritisk Forteckn. ofver Skandinaviens Hafs-Bryozoer, ivy. (1868) 
pp. 34, 203, pl. xxviii, figs, 222-225. 
