General History of the Marine Polyzoa. 361 
punctures ; surface uneven, rather coarsely granulose, usually 
a small depression (? pore) in the centre; orifice large, much 
taller than wide, arched and expanded above, somewhat con- 
tracted below, constricted a short distance above the inferior 
margin, which curves outwards; on each side of the orifice 
(or sometimes on one side only) a much elongated subspatulate 
avicularium, which originates some way below the orifice and 
slants obliquely upwards to a little above the top of it; man- 
dible long, blunt and slightly expanded at the extremity, and 
directed upwards. Owciwm rounded, somewhat prominent, 
moderate in size, surface roughened. 
A fine characteristic member of the genus, of which the size 
of the cells and the elongate avicularium are the striking 
features. 
PoRELLA, Gray. 
Porella malleolus, n. sp. (Pl. XIII. fig. 5.) 
Zowcia rectangular, disposed in linear series, depressed, 
separated by delicate raised lines; surface covered with small 
punctures and nodulous ridges; a line of larger foramina 
round the sides; orifice arched and expanded above, much 
contracted below, the margin about the centre projecting 
inward on each side, lower lip slightly curved (nearly 
straight); within it an avicularium with a hammer-shaped 
mandible. Occasionally an avicularium at one side, which 
takes its origin some way down the cell and slopes upward to 
the top of the orifice; mandible elongate, slightly expanded 
at the base, slender above it, and pointed at the extremity, 
directed upwards. Ocectum (?). 
Zoarium incrusting, whitish, of very delicate material. 
The hammer-shaped mandible of the avicularium is a 
curious peculiarity, and, when ‘elevated and standing erect 
within the lower hp, a very conspicuous one, 
SmitriA, Hincks. 
Smittia trispinosa, Johnston, vars. 
Range. Norway and Arctic seas, St. Lawrence, Mazatlan, 
North Pacific (Queen Charlotte Islands), Florida, Cape Horn, 
Aden, Adriatic, Britain, Bass’s Straits. 
Of this cosmopolitan species several varieties occur. 
i. Peristome usually not elevated, and the marginal den- 
ticle very prominent (as in the Arctic form); sometimes the 
usual triangular avicularium present, but in some of the cells 
Ann. & Mag. N. Hist. Ser. 5. Vol. xiii. 24 
