Rey. T. Hincks on the Genus Retepora. 359 
Locality. South Australia*. 
In this species the characters of the mouth are very distinc- 
tive. The shape and the minute marginal slit and the way 
in which the cell-wall in the adult is carried up on each side 
of it and hollowed out in front are all very characteristic 
points. The aviculariwm on the front of the cell is a very 
constant feature; it is sometimes depressed and sometimes 
slightly elevated above the surface. 
Perhaps, however, the most marked peculiarity is to be 
found in the tessellated condition of the dorsal surface. It is 
mapped out into distinct areas, each bounded by a raised line, 
and is covered with great numbers of the pointed avicularia, 
similar to those which are so abundant on the front of the 
zoarlum, 
5. Retepora robusta, n. sp. (Pl. XVIII. fig. 9, 10.) 
Zoartum thick and massive. Jenestre elongate-oval, large, 
separated by very wide and solid interspaces; habit of growth 
unknown. Zoowcia regularly rhomboidal, surrounded by raised 
lines, which terminate above on a level with the inferior mar- 
gin of the orifice; surface smooth, uneven, often depressed in 
thecentre. Orifice arched above; lower margin almost straight; 
no sinus ; occasionally a small oval avicularium placed trans- 
versely immediately under the lower lip, or upon it; on the 
front of most of the cells a somewhat tongue-shaped avicu- 
larium, pointing straight downwards, or sometimes placed 
obliquely, often occupying its central depression. Oowcia 
Dorsal surface vibicate, with scattered small avicu- 

laria, 
Locality. South Australia. 
This species is distinguished from all the preceding by its 
massive zoarium and large reticulations. The meshes are 
much elongated and the inosculating branches of remarkable 
width and solidity. 
There are points of agreement between it and Macgilli- 
vray’s R. porcellana. But as he has not given us a detailed 
account of its minute structure, or a figure, it is impossible 
to decide whether such agreement implies specific identity. 
His description of the avicularium which occurs towards the 
middle of the cell in R. porcellana, as having a “short man- 
dible,” is sufficiently vague; but, so far as it goes, it does not 
apply to that of the present form, which is elongate and 
tongue-shaped., 
* T am indebted for most of my Australian specimens to my friend 
H, R. W. Lemann, Esq., of Bath. 
