CELLULARIA. 339 



not its specific name from the number of the spines, but 

 from having three cells betwixt every two joints. 

 ** Aperture superior, subterminal, oval. 



3. CELLULARIA SCRUPOSA, Creeping Stony Coralline, Ellis. 



Hab. On the roots of Laminaria digitata, and on coral- 

 lines and seaweeds. Peter head, not uncommon, Mr. Peach. 

 It is common in the Firth of Forth, and in the north of 

 Scotland, but we have very seldom met with it in the west. 

 Mr. Eobert Gray has found it in abundance to the east of 

 Dunbar. Where it is found at the roots of seaweeds, it 

 often covers an inch square, creeping along the surface, and 

 attaching itself by tubulous root-like fibres ; the cells are 

 oval ; each cell has two appendages, the one in the form of 

 pincers, and the other is furnished with a long moveable 

 bristle. 



4. CELLULARIA REPTANS, Ellis. 



Hab. On corallines, seaweeds, etc.; common. 



This is pretty like the preceding, but the tufts are larger. 

 The branches are dichotomous; the cells have an oblique 

 opening, armed with four or sometimes five short spines. 

 The colour is lighter than that of the preceding; with us it 

 is light grey, and not unfrequently tinged with red. It is 

 very abundant, on the coast of Ayrshire, on Halidrys sill- 



