STRUCTURE OF OPHIURUS. 195 



slender rays, which, both in their general appearance 

 and in their movements, strikingly remind the spec- 

 tator of the tail of a serpent, from which circum- 

 stance these creatures have in fact derived their 

 scientific designation (o</>9, a serpent ; ovpo?, a tail) . 



The disc is circular or sub-angular, and the mouth, 

 which is situated in the centre of the under surface, 

 pentagonal and very dilatable. The upper surface is 

 in some species nearly smooth, in others clothed with 

 very minute scales or spines ; but its chief variety is 

 in colour, and in the distribution of the colours, some 

 of them being exceedingly beautiful. 



Instead of the elaborate apparatus of suckers spe- 

 cially serving for the movements and adhesion of the 

 Asterias, the rays of the Ophiurus consist of jointed 

 segments, and are provided with an infinity of spiny 

 processes arranged along their sides, which, together 

 with their accessory parts, are very different in differ- 

 ent species. The rays also are covered by scales, 

 which present great diversity of form, arrangement, 

 and distribution. 



The rays of the Ophiuri are extremely liable to 

 mutilation, partly owing to their length and slender- 

 ness, and partly because they so easily become en- 

 tangled among foreign substances; they are, how- 

 ever, speedily renewed, although the reproductive 

 faculties seem less energetic in these creatures than 

 in some of the preceding races of Star-fish. 



The vigour and the dimensions 01 the Ophiurus 

 seem to depend very much on the places where it 

 dwells, and the facility of obtaining subsistence. 

 Some live in deep water ; multitudes are met with 



K2 



