298 Z0ANTHIDJ3. 



Tentacles. Twenty-eiglit (twenty-four in less mature specimens), arranged 

 in two rows, fourteen in each : those of the inner row correspond to the 

 marginal teeth, those of the outer are intermediate. They are sub-equal, 

 taper, bluntly pointed, and, when extended, about equal in length to the 

 diameter of the column, hollow, not warted, with thick walls, which, in 

 contraction, fall into transverse or annular corrugations. They are pro- 

 truded in a brash, but, when fully expanded, spread out horizontally. 



Mouth. Lip sharp, much crenated, protruded after feeding. 



Colour. 



Investment of root-band and column. Pale brown, the hue of the sand. 



Column. Beneath the investment, transparent and colourless. 



Disk. Pellucid reddish-grey, dusted with excessively minute white 

 specks. 



Tentacles. Translucent, nearly colourless ; but each has a small mass of 

 opaque white pigment on the internal surface, just at the tip : the aggre- 

 gation of white points has a pretty effect. 



Mouth. Lip opaque white. 



Size. 



None that I have seen alive exceeded one-eighth of an inch in diameter, 

 and about thrice that height in extension. In contraction the button is 

 usually about a line in height. Mr. Holdsworth has obtained specimens 

 much larger than these. 



LocALiTr. 



The extreme northern and southern points of the British Islands, North- 

 umberland, and various other points of our coast; deep water; on stones 

 and shells, and free on the sea-bottom. 



Varieties. 



a- Linearis. The condition above described, in which the root-band 

 creeps in a narrow ribbon over stones and shells. Cornwall and Devon. 

 (Plate x. fig. 5.) 



/3. Diffusus. The root-baud spread over the surface of a shell as a 

 continuous carpet, whence the polypes spring, irregularly crowded together. 

 Northumberland. (Plate ix. fig. 10.) 



y. Liber. Unattached. The root-band forming a free cylinder, exactly 

 resembling the column of the polype, and of the same diameter. The 

 polypes in this case branch irregularly from the cylinder, aud terminate 

 both its extremities. Shetland. (Plate ix. fig. 9.) 



If we selected a single specimen of each of these varieties, 



