Polyzoa of the St. Lawrence. 155 
differs remarkably in appearance from the rest of the cell, 
which is of a brown colour and thickly covered with pores. 
It is smooth, dense, and of a whitish colour, showing very 
distinctly on the dark front wall. The avicularium lies across 
the upper part of it, immediately under the lower margin of 
the orifice, slanting slightly upwards. ‘The whole structure 
probably represents the umbo of the normal form. Its effect 
on the general appearance of the cell is very striking. 
The orifice in this species is wide and well arched above, 
but below the articular denticles, which are placed more than 
halfway down, it narrows off and terminates below ina curved 
line. The structure of the orifice would seem to connect it 
with the genus Schizoporella rather than Lepralia. 
Membranipora armifera, Hincks. (Pl. VIII. fig. 4.) 
Membranipora armifera, Hincks, “ Contributions towards a General 
History of the Marine Polyzoa,” ‘ Annals,” ser. 5, vol. vi. p. 82, pl. x1. 
fig. 5. 
Some time since I described a species of Membranipora from 
the St. Lawrence under the above name; but it now appears 
that the specimen was immature on which the description 
was founded. Fortunately the occurrence of the perfect form 
enables me to revise and complete the diagnosis. 
Zoecia ovate, quincuncial, wholly membranous in front, 
margin rather wide, the inner border crenulate, two spines at 
the top, on each side (or sometimes on one only) a little 
below the upper margin an acute avicularium, placed obliquely 
on the top of a prominent bracket-like support, carinate in 
front, mandible directed downward, a tall and very stout 
articulated spine rising from the margin close to one or (occa- 
sionally) both of the lateral avicularia, immediately below 
the cell a large mounted avicularium. Occcum rather large, 
much broader than high, surface smooth and entire, a promi- 
nent rib across it a little above the oral arch, and at the top a 
large elongate avicularium placed obliquely and stretching 
along one side of the cell above, mandible pointed. 
Hab. On shell and stone, and incrusting Flustra membra- 
naceo-truncata, Smitt. 
Commonly only one of the lateral avicularia is present, and 
the large articulated spine takes the place of the other. In 
some cases both avicularia are present, each with an attendant 
spine. When the ocecium is developed it adheres to the 
avicularium at the base of the cell above, which appears as if 
it were a part of it. 
This species is nearly allied to A, untcornis, Fleming. 
