294 A. EF. Verrill—The Bermuda Islands; Coral Reefs. 
the column, especially on the convex side, but these are sometimes 
nearly obsolete in small specimens. A circle of about 10 to 12 
tubercles surrounds the infolded portion of the summit in contrac- 
tion; the summit is covered by numerous convergent sulcations. 
The greater part of the column is covered with longitudinal and 
transverse sulcations, most conspicuous in strongly contracted alco- 
holic specimens ; the tubercles are lacking on the concave side and 
toward the base. The column is translucent, so that the mesenteries 
show through the wall. The tentacles are about 40 to 46. Perfect 
mesenteries about 20. Height 20 to 40™™; diameter of column 
141 
Figure 139.—Isaurus tuberculatus, smoother var., contracted. x14. 
Figure 140.—The same, rougher var., strongly contracted. x14. Drawn by 
the author from preserved specimens. 
Figure 141.—Parazoanthus parasiticus, } nat. size: a, parasitic on ‘‘ tube- 
sponge”; b, parasitic on Hircina? Phot. A. H. V. 
usually 8 to 10™™ in contraction. Our best specimen is 40" high 
and 9™™ in diameter as contracted; it is much smoother than some 
of those figured. It differs generically from Zoanthus chiefly in 
having but one sphincter muscle instead of two. The color of the 
column, disk, and tentacles. in life is buff or ocher-yellow. It is not 
uncommon on the Bermuda reefs and is also found throughout the 
West Indies. ; 
McMurrich considered the Bermuda form (as tuberculatus) a 
species distinct from that of the Bahamas. To me the differences 
noted seem to be individual variations. 
