INVERTEBRATE ANIMALS OF VINEYARD SOUND,. ETC. 399 



some closely allied genus, but of this only the asexual form lias occurred, 

 and it lias not yet been carefully studied. This becomes nearly an inch 

 long and quite slender. The body is white, with about fifty aunulations 

 of bright purplish red between the segments, but sometimes a red ring- 

 is absent, leaving wider white bands ; the lateral appendages are simple, 

 and each has a dot of red on the anterior side j the head is orange, with 

 four dark red eyes. 



Of Mollusks there are but few species among the higher groups which 

 do not also occur on the rocky shores at low-water, but of the As- 

 cidians and Bryozoa we find numerous additional species. The Gas- 

 tropods are represented by the large Fulgur carica (p. 355, Plate XXII, 

 tig. 124) and Sycotypus ccmaUcuIatus, (p. 355 j) also by the " drill," Urosal- 

 plnx cinerea, (p. 306, Plate XXI, fig. 116,) which is usually abundant in 

 shallow water ; Astyris lunata (p. 106, Plate XXI, fig. 110) is abundant on 

 the hydroids and algjB ; A. zonalis^ (Plate XXI, fig. Ill,) which is an allied 

 species, of larger size and with plainer colors, is sometimes met with, but 

 is rare in this region. It takes its name from two narrow spiral zones of 

 white that usually surround the whorls. The Cntclbidum striatum 

 (Plate XYIII, figs. 125, 126) is often met with clinging firmly to the rocks 

 and stones. 



The Leptochiton apiculatus (Plate XXY, fig. 167) is one of the most 

 .characteristic and common species on rocky and gravelly bottoms; 

 this also adheres firmly to the stones and dead shells, and its grayish or 

 dirty whitish shell, often more or less stained, blends its color with 

 that of its surroundings in a way that might deceive the fishes them- 

 selves. The back is covered with a series of movable plates, so that 

 when removed the animal can curl itself into a ball, like a "pill-bug," 

 (OniscuSj) or like an armadillo, a habit that it shares in common with 

 the scaly annelids, Lepidonotiis and Rarmothoe] which live in the same 

 places with it. The flexibility of the shell also enables the chitons to 

 adapt themselves more closely to the uneven surfaces of the rocks than 

 they otherwise could. More rarely the Leptochiton ruber (Plate XXV, 

 fig. 166) is met with, though farther north, as in the Bay of Fuud^', this 

 is a very common species, while the apiculatus is quite unknown there, 

 being decidedly southern in its range. The ruber is, as its name implies, 

 a red species, and its colors are usually bright and beautifully varied 

 with lighter and darker. Its bright color would seem at first a fatal gift, 

 calculated to attract the attention of passing fishes, which are always 

 fond of such food, but when we examine its habits more closely we find 

 that it lives almost exclusively on and among rocks that are incrusted 

 by the curious stony algae, known as " nuUipores," {Lithothamnion poly- 

 morplmm^) which are red in color, but of various shades, and often com- 

 pletely cover the rocks with irregular red incrustations, over lar^e areas 

 in shallow water, especially on the coasts farther north, so that this 

 shell and a larger species, (0. marmorei^s,) usually associated with it, 

 are admirably adapted by their colors for living and concealing them- 



