360 Rey. T. Hincks on the Genus Retepora. 
The very regular rhomboidal shape of the cell in R. robusta, 
and the way in which its bounding lines extend only to the 
inferior margin of the orifice and do not embrace the mouth 
itself, are distinctive points. Its most striking characteristic, 
however, is the stoutness of its habit, by which it can be at 
once distinguished from all the other southern species with 
which I am acquainted. 
The species which follow have already been described ; but 
I venture to supply a fuller account of them than we have 
from the authors who have previously noticed them. In 
studying this very difficult family I have vividly realized the 
necessity of thorough and minute diagnosis, if we are to 
escape the very serious evils of doubtful identification and a 
burthensome synonymy. 
1. Retepora monilifera, Macgillivray*. (Pl. XIX. figs. 1-5.) 
Zoarium regularly cup-shaped, or much convoluted, and 
forming a number of irregularly shaped cavities, the smuous 
and anastomosing walls of which give a very intricate appear- 
ance to the surface; surface minutely granulated. enestre 
very small, narrow-oval ; interspaces broad. Zoowcia sub- 
cylindrical, distinct, flattish ; orifice (primary) arched above, 
slightly curved outwards below, broader below than above, 
with a minute sinus on the inferior margin ; secondary orifice 
(formed by the elevation of the cell-wall) orbicular, with a 
deep looped sinus in front, on each side of which is an as- 
cending process, one of the two bearing on its inner side a 
small avicularium, the mandible directed upwards ; a tall and 
stout jointed spine on one side just above the avicularium. 
Small oval avicularia distributed over the zoarium. Tall 
and stout aviculiferous processes, expanding downwards, 
often present in great numbers; the avicularium placed on 
the front with a pointed mandible. Oowcia large, prominent, 
subpyramidal, with a granulated rim above the upper edge of 
the aperture, from the centre of which a somewhat clavate 
band, also granulated or beaded, extends upwards, almost to 
the top of the ovicell. Dorsal surface dense, minutely granu- 
lar, slightly vibicate, with scattered small oval avicularia. 
Locality. South Australia. 
On the young marginal cells the primary orifice with its 
minute sinus is met with; in the older portions of the colony 
#* “Notes on the Cheilostomatous Polyzoa of Victoria and other parts 
of Australia,” by P, H. Macgillivray, A.M., M.R.C.S. (Trans, Phil. Inst. 
of Victoria, vol. iv. 1860, p. 168, pl. iii. figs. 6-9), 
