a General History of the Marine Polyzoa. 13 
Oacium very large, covering almost the whole of the cell 
above it, rounded, often traversed by raised white lines, with 
one or more projecting pointed processes on each side in front, 
overhanging the opening, and opposite to them on the lower 
margin two (sometimes more) strong conical teeth; surface 
covered with large nodules and punctured ; orifice of the ovi- 
celligerous cell very large, elongated transversely, with a 
slightly sinuated lower margin. 
Loc. Bass’s Straits, 40 fms., common. 
The zocecia are often very irregularly disposed, turned in 
all ways, and variable in shape. They are sometimes much 
more convex than is usual, and ovate, losmg much of the 
normal appearance. ‘These irregularities occur amongst the 
secondary cells, which are developed upon the primitive layer. 
The typical character is very constant in the primaries. 
S. triangula belongs to the S. linearis group. 
Schizoporella tumida, n. sp. 
(Pl. I. fig. 3.) 
Zocecia ovate, disposed in linear series, which radiate in all 
directions from a centre, perfectly smooth, moderately convex ; 
orifice arched above, lower margin with a rounded sinus in 
the centre; peristome not raised; immediately below the 
orifice a pouch-like swelling, bearing on the upper surface 
a small rounded avicularium; frequently an ovate rising on 
one side of the cell, extending from the orifice down a consi- 
derable portion of its length, bearing on its upper extremity 
an immersed avicularium, with pointed mandible directed 
downwards. Owciwm globose and prominent, with a smooth 
surface. 
Loc. Bass’s Straits, on shell. 
This species bears some resemblance to the 8. marsupium 
described by Mr. Stuart Ridley in his valuable paper on the 
‘Alert’ collections from the Straits of Magellan and Pata- 
gonia, but is, I think, distinct. Mr. Ridley (Proc. Zool. 
Soc. Lond. for Jan. 4, 1881, p. 48, pl. vi. fig. 6) identifies 
his species with the Lepralia marsupium of MacGillivray ; 
but the latter is, I believe, a Porella very nearly allied to 
P. minuta of our own coasts, and extremely abundant in Bass’s 
Straits. MacGillivray’s diagnosis is unfortunately brief, 
giving no account of the shape of the mouth; so that it is by 
no means easy to determine the species which he had in view. 
On the whole, however, it agrees better with the Porella so 
common in South-Australian waters than with any other form 
I know. 
