198 MARINE INVERTEBRATES 
A, hispidum. One of the most common species found inerusting 
the fronds of Ascophyllum at low-water mark. It forms fleshy, brown, 
soft crusts of moderate thickness, and has spines scattered over the 
otherwise smooth and glistening surface. The cells are inconspicuous, 
and each one has five long rigid bristles. Habitat, Long Island Sound 
to Greenland. 
A. parasiticum. It forms thin, earthy crusts on alge and hydroids. 
The surface is porous; the cells are distant and arranged irregularly, 
and seem as if composed of sand cemented with mud. 
Genus Vesicularia 
V. dichotoma (Valkeria pustulosa). This species grows in clus- 
ters of crowded slender stems, which branch in a forking manner, the 
branches dividing in different planes, making a tree-like form one to 
three inches high. At the points where the branches divide is a dark, 
opaque substance, and at these points also the cells are crowded in clus- 
ters of spiral rows and are greenish-brown in color. The dark spots 
are in marked contrast to the white translucent substance of the rest 
of the stem, giving a spotted aspect to the whole. (Plate LI.) 
V. custata. Delicate, thread-like, jointed stems, with slender oppo- 
site branches; cells small and elliptical, arranged mostly in clusters. 
Found creeping like a small dodder-plant over other polyzoans, hy- 
droids, and seaweeds. 
SUBCLASS ENTOPROCTA 
Genus Pedicellina 
P. americana. <A very small species. Club-like zocecia rise from 
slender, white, creeping stems; tentacles roll up instead of retracting 
into the cups. Found on hydroids, other polyzoans, and alge. 
