[315] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 21 



species, found in the same situations, is the Mcera levis SMITH ; this is 

 whitish in color, with black eyes. 



Two species of the genus AmphithoSsAtoo live under rocks at low water, 

 but these, like the other species of this genus, construct tubes in whidi. 

 they dwell. The Amphithoe maculata (Plate IV, fig. 16) is much the larger, 

 and constructs large, coarse tubes of gravel, bits of sea-weed, &c., and 

 attaches them in clusters to the under sides of stones. They often leave 

 their tubes, however, and may be found free among the weed or under 

 stones. The color is generally dark green, though sometimes reddish, 

 and there is often a series of light spots along the back, and the whole sur- 

 face is covered with minute blackish specks $ the eyes are red. The 

 second species, Amphithoe valida SMITH, is much smaller, being gener- 

 ally less than half an inch long. It is usually bright green in color, and 

 has black eyes. It often lives among the bright green fronds of Ulva 

 latissima, and its color is nearly that of the Ulva. 



Another amphipod, resembling a small Gammarns^ about half an inch 

 long, and light olive-brown or yellowish brown in color, is sometimes 

 found in large numbers swimming actively about in the larger tidal 

 pools, and occasionally darting into the growing sea-weeds for rest or 

 concealment. This is the Calliopius Iceviusculus. It also often occurs 

 in vast numbers swimming at the surface, far from land, not only in the 

 sounds and bays, but out at sea, as for instance in the vicinity of St. 

 George's Bank and in the Gulf of St. Lawrence, where it is equally 

 abundant. It is devoured in large quantities by numerous fishes. 

 The Hyale littoralis occurs near high-water, among algae, and in pools. 



The Isopods are also well represented on the rocky shores. One 

 of the most common is the Sph&roma quadridentata, (Plate V, fig. 

 21,) which bears some resemblance, both in form and habits, to the 

 "pill-bugs, ? which live upon the land. This species is found in abun- 

 dance under stones and rocks, or creeping slowly about among the branches 

 and roots of sea-weeds, on their sides and upper surfaces, from low- 

 water mark nearly up to high-water mark. In color it is exceedingly 

 variable, for no two can be found that are alike $ but the colors, consisting 

 of irregular blotches and dashes of dark gray, light gray$ slate, greenish, 

 and white, are so blended as to imitate very closely the colors of the bar- 

 nacles and gray surfaces of the rocks where they live, and no doubt 

 they derive considerable protection from their enemies by these imita- 

 tive colors. When disturbed they curl themselves up in a ball and fall 

 to the bottom. 



Another smaller and much more active species, which has a more 

 slender form, is found in vast numbers creeping actively about over the 

 rocks and barnacles, and especially beneath rocks and drift-wood. This 

 is the Jccra copiosa. It is also excessively variable in color, but shades 

 of green, gray, and brown predominate, and cause it to imitate very ef- 

 fectively the surfaces of the rocks covered with small green algre, where 



