a General History of the Marine Polyzoa. 155 



seem to be that the zocecium is divided into two parts, and 

 that " a narrow transverse portion " of the front cell-wall, " a 

 little distance behind the mouth and in front of the elevated 

 part," is deficient in calcareous matter and entirely membra- 

 nous. On reexamining my specimens I find that a membra- 

 nous wall closes in the whole of the aperture, bearing the oral 

 valve at the upper extremity, and extending almost to the top 

 of the elevated portion of the cell. Beneath the oral valve is 

 an elliptical orifice with calcareous margin filled in with mem- 

 brane and having a circular opening in the centre ; from the 

 edge of this inner orifice a calcareous wall passes down to a 

 fissure extending transversely across the cell, and probably 

 marking the termination of the true zocecium. Below the 

 fissure is the wall of the elevated part of the cell, which is a 

 strong box. Towards the base of tliis Avail a tubular process 

 projects into the fissure, probably forming a communication 

 between the box and it. The precise significance of this 

 structure can only be determined by an examination of living 

 specimens ; but it seems to form a good basis for a new generic 

 group. 



One curious peculiarity of this species should be noted. 

 The colonies, which always seem to encircle the stems of 

 certain alg£e, commence with a (transverse) row of elongated, 

 narrow, quadrangular cells, having the front entirely closed 

 in with membrane, destitute of orifice, and of all the charac- 

 teristic structure of the adult ; this row is followed by a 

 second, in which the cells resemble generally those in the 

 first, but are much shorter ; and from these the normal zooecia 

 originate. 



Family Microporidse. 



Genus Vinculaeia (part), Defrance. 



Vincularia ahyssicola, Smitt. 

 (PI. X. fig. 4.) 



This form I had figured from a specimen incrusting a small 

 fragment of coral, as (probably) a new species of Setosella ; 

 and only ascertained subsequently that it was identical with 

 Vincularia abyssicola of Smitt, I mention this to show how 

 essentially Membraniporidan the zooecial character of this 

 generic type is ; in its incrusting state it is impossible to 

 distinguish the present species from Setosella. Whether its 

 peculiar habit of growth in the adult state (the zooecia are 

 arranged so as to form erect, cylindrical stems like those of 

 Cellaria, but unjointed) entitles it to generic rank is a ques- 

 tion to which different answers may be given ; but we indicate 



