292 HISTORY OF BRITISH ZOOPHYTES. 
the extremities; aperture lateral, near the distal end. Polypes 
Ascidian.—Johnston. 
1. Hrpporuoa catenuLaria, Professor Jameson. (Plate 
XV. fig. 54.) 
Hab. On shells, especially bivalves, from deep water. 
This is a very handsome little coralline. Dr. Johnston 
very properly describes it as “formed of a series of cells 
connected like a string of bugles; cells oval, widest and 
rounded anteally ; its aperture oval, with a plain thickish 
rim placed near the top.” Mr. Gray states, that when 
alive “it appears like dew-drops, and is easily separated 
from the shell by a pin, but is strongly attached when dry.” 
We have observed this, and also what Dr. Johnston men- 
tions, that in this state (when dry we suppose) the aperture 
of the cells is sometimes closed by a membrane. This was 
very evidently the case with respect to many of the largest- 
sized examples we ever met with. They were on the valves 
of Pinne from island of Coll. ‘The cells were large, and 
the branches, having full scope, covered about three inches 
of the shell in length by about an imch and a half in 
breadth, and many of the cells had this membranous cover- 
ing of the aperture by a calcareous deposit rendered as 
thick as the cells. 
