REPORT ON THE POLYZOA. 
175 
parted by thin raised septal lines ; surface longitudinally wrinkled ; a row of distant 
pores near the border and a few others sparsely scattered on the front. Peristome 
tubular, curved forwards nearly at a right angle. Median pore usually subtubular, 
sometimes depressed, immediately below the peristome. Avicularia small, circular ; 
slightly raised, sparsely disposed on the front and sides of the zooecia. “ Ocecia terminal, 
slightly raised, transversely elliptical, with a striated surface,” Hincks. 
Habitat. — Station 23, off Sombrero Island, North Atlantic, 450 fathoms, Pteropod 
ooze. Station 13, lat. 21° 38' N., long. 44° 39' W., 1900 fathoms, globigerina ooze. 
[Norway, Finmark, between Norway and Spitsbergen — lat. 77° 5' N., long. 10° 3' E., 
600 fathoms — Chydenius ; Gulf of Florida, very abundant, Pourtales ; off the coast of 
Portugal and the Azores, Smitt ; Shetland, Barlee]. 
In habit of growth this species varies a good deal, and according to Prof. Smitt it 
would appear to be more or less dimorphous, occurring in a lepralioid or alysidotal form, but 
of this no indication is afforded in the specimens that have come under my notice. And if 
one may be allowed to judge simply from Prof. Smitt’s figures, I should be much inclined 
to doubt, with the greatest deference to him, whether his figures (Joe. cit.) fig. 143, and the 
two lowermost zocecia in fig. 144, really form part of the Tessaradoma at all, or have 
merely become accidentally associated with it. The latter figure at any rate might 
well be regarded as Lepralia ( Porina ) ciliata. 
With respect to the median pore, one of the Challenger specimens presents an appear- 
ance which may perhaps afford some indication of the function of the opening in this 
situation. In this instance the slender tube (fig. 8e) rising from the pore is quite perfect, 
and slightly dilated at the end ; through this short tube a cylindrical chitinous rod or tubule 
of a dark brown colour protrudes, upon the extremity of which is firmly affixed a small 
Rotalina. From this it would seem allowable to surmise that in some cases the so-called 
median or central pore may serve for the emission of a prehensile organ, capable of 
attaching itself to foreign bodies, and thus performing what may be supposed to be the 
function of an or din ary avicularium. But there can be no doubt, as I have observed 
above, that the nature and true homologies of these median pores are very various, and 
for the most part at present wholly unknown. 
I have not as yet been able myself to perceive the primary mouth in Tessaradoma 
boreale, but from Prof. Smitt’s figure (Joe. cit., pi. xxiv. fig. 29), it would appear to be 
circular, with a central opening through a hymen-like membrane- — a very curious con- 
dition if it be correctly figured. The very delicate operculum, however, is circular 
with a thin chitinous thickening on each side and it is not perforated. 
