BRITTLE-STARS 215 



Some species may be found near low-water mark under stones 

 and in clusters of mussels, and often in seaweeds, thrown up 

 from deep water, on the shore. 



ORDER EUEYALIDA 



GENUS Astrophyton (Plate LV) 



A. Agassizii. This very singular ophiuran is commonly called the 

 basket-fish, from its resemblance to a basket when the tentacles are 

 rolled up. Its body is covered with skin instead of calcareous plates. 

 The body is thick and somewhat circular in form, with elevated radi- 

 ating ridges on the upper side, and the skin is marked off in star-like 

 divisions. From the margin of the body extend five arms, which at 

 once divide in a forking manner ; each section again divides, and this 

 division in pairs (dichotomous division) continues until the ends of the 

 arms have become very numerous and attenuated. The arms are carried 

 curled up or straight at will. In moving, the animal seems to walk on 

 these branches as if on tiptoe, and in this position it forms a kind of 

 net which entraps prey. The arms and prominent parts of the disk are 

 yellow, and the depressed or membranous parts brown. Astrophyton is 

 six to eighteen inches in diameter. It is found off the northern New 

 England coast. 



ORDER OPHIURIDA 



GENUS Ophiopholis 



O. aculeata. This is a common species, found in shallow water on 

 the North Atlantic coast. A similar or perhaps identical species occurs 

 on the North Pacific coast. It is spotted purple or variegated in color. 

 The upper surface of the body is covered with plates variously arranged, 

 sometimes in the shape of a star, and each one is surrounded with small 

 spines. The under side of the egg-sacs is covered with small spines. 

 These sacs open by slits on each side next the arms, and have a rounded 

 appearance, bulging out between the arms. The arms, which are long 

 and attenuated at the ends, have on the upper side transverse oval plates 

 surrounded by a border of flat, roundish granules. Sometimes the 

 plates are divided into two or three pieces, when they are similarly bor- 

 dered with granules. The arms are fringed with rows of thick, com- 

 pressed, obtuse spines, generally six in each row. The under sides of the 

 arms have large quadrangular plates slightly separated from one another 

 and extending across the whole surface in regular, even rows. 

 (Plate LV.) 



GENUS Amphiura 



A . squamata. This very delicate species, found on shelly bottoms 

 below low-water mark from New Jersey northward, has a body less 

 than one quarter of an inch in diameter, with arms two inches or more 



