APPENDIX. 297 



rounded at the tip, where a small slit marks the situation of its 

 toothless mouth. There are no eyes. The third and fourth seg- 

 ments are elongated, but the others are nearly equal, being, when at 

 rest, about one-eighth of an inch in length and in breadth ; the pro- 

 No. XLVIII. — Meckelia annulata. 



a. Natural size, and in a state of quiescence, 

 shaded, to show the lateral pale lines. 



b. The head slightly magnified and 

 c. A small portion of the tube. 



portions, however, varying much according to the degree in which 

 the body, or particular portions of it, are extended. When mag- 

 nified, the margins appear finely crenulate. The anus is simple and 

 terminal. 



Meckelia annulata was found within a coarse tube attached to an 

 old'valve of the Venus islandica of British authors. The tube was 

 about 4 inches long, formed of a membrane, smooth, and iridescent 

 internally, but coated on the outside with gravel and pieces of broken 

 shells, and open at both ends. 1 have found a very different worm 

 in a similar tube ; so that a doubt may, perhaj)s, be entertained, 

 whether the Meckelia fabricates it of itself, or is merely a tenant 

 at will. From the body being distinctly annular, the worm is brought 

 in contact with the Annelides ; but its softness, the want of feet or 

 bristles, the apparent simplicity of its structure, and its resemblance 

 to the tapeworms, and more especially to the Linens longisshnus of 

 Sowerby, favour its claim to be placed among the Vermes. 



Another, and a very fine specimen, was of a chocolate-red colour, 

 tinted purplish-red on the sides, and the ventral surface was of the 

 latter colour throughout ; but the most remarkable difference was 

 that there was a white line down the middle of the belly as distinct 

 as that down the back. 



All the specimens seen by Sir J. G. Dalyell had the abdominal 

 white line. This is exactly opposite the dorsal line, so that the lines 

 divide the body longitudinally into four equal spaces. The worm is, 



