INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 487 



agilis,) which it somewhat resembles in form. The color is very variable ; 

 it is often bright yellowish green, but frequently dark green, brownish 

 green, or brown. 



The Nereis virens (p. 317, PI. XI, figs. 47-49) is very abundant in bur- 

 rows beneath the rocks. The males of this species, six to ten inches or 

 more in length, and of a dark green color, were found at Watch Hill, 

 April 12, in great numbers, swimming about in the pools of water among 

 the rocks, with an undulatory motion, and discharging their milt in large 

 quantities. Yarious other Annelids burrow or build tubes beneath the 

 stones. A.planaria and Leptoplana folium creep over their lower sur- 

 faces. 



Attached to the stems of Fucus at low-water, -several Hydroids may 

 usually be found, but the Sertularia pumila (p. 327, PI. XXXVII, fig. 

 279) is by far the most abundant. The Obelia geniculata is also very 

 common, attached to Laminaria and other algae. Yarious Bryozoa occur 

 attached to stones and to Fucus and other algae. The Alcyonidium 

 Mspidum (p. 312) is one of the most abundant species, and usually in- 

 vests the stems and fronds of Fucus vesiculosus, but also often covers 

 broad surfaces of the rocks. The A. hirsutum is often associated with 

 the preceding species on the rocks; it forms broad, thin, soft crusts, cov- 

 ered with small soft prominences, but is without the spines or bristles 

 seen in the latter. The Zooids are also much smaller. 



The Farrella familiaris is a singular and delicate species, which occurs 

 both on the under side of rocks and on alga3. The body is small, fusi- 

 form, attached by a long and very slender, flexible pedicel. When it 

 surrounds the stems of small algae, the whitish pedicels project outward 

 in all directions, and thus produce the appearance of a delicate chenille- 

 cord. This is a northern and European species. It was also dredged on 

 Saint George's bank in 1872. 



List of species found on the outer roclcy sliores. 



ARTICULATA. 



Crustacea. 



Page. 



Cancer irroratus . , 486 



Cancer borealis • 486 



Panopeus depressus 312 



Panopeus Sayi 312 



Homarus Americanus. 492 



Orchestia agilis 315 



Hyale littoralis . . . .' 486 



Calliopius laeviusculus 315 



Gammarus ornatus 486 



Gammarus annulatus 486 



Page. 



Gammarus marinus 486 



Amphithoe maculata 486 



Amphithoe, sp 486 



Caprella, sp 316 



Jaera copiosa . , 486 



Idotea irrorata 486 



I. phosphorea 316 



Erichsonia filiformis 316 



Balanus balauoides 486 



