308 A, E. Verril—The Bermuda Islands; Coral Reefs. 
(fig. 148), the intervals between them being generally less than their 
diameters, and often much less on the distal part of the branchlets, 
but sometimes, when partly contracted, on the large branches, they 
are not very close in external appearance. 
The polyps in expansion are very prominent and much larger than 
in P. flexuosa, and so close together that their tentacles overlap and 
entirely conceal the ceenenchyma. They are translucent and dull 
yellowish or brownish, disk and tentacles yellowish brown. The 
tentacles are long and tapered, with 10-12 short pinne on each 
side (fig. 148). They have but little activity in contracting, and 
=? 
153 154 155 
Figure 153.—Plexaura Esperi: a, small purple spindles and double spindles of 
inner layer ; 6, small purple spicules of middlelayer. Fig. 154.—The same: 
small purple spicules of middle layer. Fig. 155.—The same: white spicules 
of surface ; c, c, foliated clubs ; d,d, irregular forms; g, h, double spindles, 
x70. Drawn by A. H. V. 
generally remain expanded when preserved, but they are able to 
contract slowly and completely. They contain no spicules in the soft 
body nor in the tentacles. 
The axis is hard and rigid at base, but in the branches it is black 
and flexible. It is the one usually made into riding whips by the 
fishermen. * 
The cenenchyma is thick and apt to be friable, unless dried with 
care. It should be previously soaked in alcohol or formalin, for the 
exsert polyps are so numerous and large that they often cover up 
and disfigure the surface as well as prevent it from drying rapidly. 
In life the ceenenchyma is usually light yellow or brownish, but 
when dried the surface often becomes pale straw-yellow or purplish 
gray, or nearly white, due to large white fusiform spicules, but the 
* These generally consist of two or three long terminal branches twisted 
together and polished. 
