198 MARINE INVERTEBRATES 



A. hispidum. One of the most common species found incrusting 

 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. parasiticwm. It forms thin, earthy crusts on algae 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 spot s 

 are in marked contrast to the white translucent substance of the rest 

 of the stem, giving a spotted aspect to the whole. (Plate LI.) 



F. 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 algae. 



