278 A, E. Verrill—The Bermuda Islands; Coral Reefs. 
_ The base, which is often expanded and lobulated, adheres very 
closely to the rocks, and is very liable to be injured in removal. It 
sometimes secretes an epidermal basal cuticle. The body, in full 
expansion, is narrow below, but spreads out toward the disk into a 
cup-like or vase-like form, or even into a broad salver-shape, with 
the thin rim of the broadly distended disk often horizontal, or even 
reflexed, and frequently undulated. The exterior is very smooth 
and lubricous, and when irritated it secretes a great amount of tena- 
cious mucus, but in partial contractions the wall is often longitu- 
dinally lined or grooved, corresponding to the mesenteries, and 
sometimes transversely wrinkled, but never has verruce or suckers. 
The broad disk may be concave or convex, according to state of 
expansion, and is often flexuous; the mouth is generally raised on a 
broad conical elevation ; the lips have numerous (48-60) small lobes 
and grooves, but no distinct gonidial grooves. Several short, 
rounded or wart-like tubercles surround the mouth. 
Then there is a nearly naked smooth area, beyond which numer- 
ous radial rows of disk-tubercles run out toward the bases of the 
marginal tentacles, but leave a naked zone in front of them. The 
disk-tubercles vary in form and size. Twelve primary rows can 
usually be distinguished by their larger size, greater complexity, 
and often by their white or lighter color. The proximal and distal 
tubercles of the larger rows, and all of those in the smaller rows are 
simple, rounded, mammiform, or verruciform, and in specimens of 
less than an inch in diameter all are usually simple. But in the 
larger specimens, 5 to 8 or more of those in the middle part of the 
larger rows are lobulated, each bearing 3 to 6, or even 8, irregular, 
short, blunt, divergent digitations or lobules, while those more distal 
become gradually smaller and simple. There may be 12 to 20 or 
- more in a radial row. 
The margin is thin and bears a single row of short simple, unequal 
tentacles, in which groups of one to three larger ones alternate with 
groups of three or four smaller ones, somewhat irregularly. 
The body is but little contractile, and the disk cannot be enrolled, 
but may be incurved. The internal structure is peculiar in several 
respects. 
The color of the column varies greatly. It is often greenish 
brown below, becoming chocolate-brown or umber-brown above, and 
usually finely lined with paler, and frequently flecked with whitish 
or pale spots; specimens that are olive-green, purplish, or fawn-color 
are also common ; they are usually paler near the base. 
