ARGULUS. 249 



peculiar construction. They are in the form of short, 

 hollow, flexible cylinders ; the pedicle by which they are 

 attached to the animal being thick and muscular, and the 

 extremity terminating in a broad, circular, horizontal rim, 

 almost cartilaginous, having a membranous margin, fringed 

 all round with numerous rays, which, according to Dana 

 and Herrick, are many-jointed. Four muscles are attached 

 to the base of each of these organs, and extend up the 

 sides. By this organization the animal can make use of 

 them as real sucJ^ers, or cupping-glasses, to fasten itself 

 to the fish upon which it lives, and also to walk with, 

 when it wishes to change its position. By contracting 

 these muscles, it can exhaust the cavity of the sucking- 

 disc, producing a vacuum, and thus enabling it to adhere 

 firmly to the surface upon Avhicli it is placed. When it 

 wishes to change its place, it relaxes the muscles first of 

 one sucker, carrying if forwards, and then the other, alter- 

 nately, as was long ago observed by Ijoefling. The second 

 pair of ambulatory legs, or third pair of foot-jaws (t. XXXI, 

 f. f/), arises immediately below these suckers, and is very 

 different in conformation. They are somewhat cylin- 

 drical, and are composed of five articulations. The first 

 two are much larger than the others, have their surface 

 roughened with small spines ; and at the base of the first 

 joint, we see three strong teeth. The last joint gives off 

 at its extremity two small hooks. These organs are called 

 the prehensile feet by Dana and Herrick, and no doubt 

 they do assist the animal to secure itself more firmly in 

 its position. The natatory feet are four pairs, arising in 

 a series on each side of the thorax, and partly covered by 

 the lateral portions of the carapace. The first three pairs 

 (t. XXXI, f. /i,i,) consist each of a large fleshy peduncle, or 

 basilar portion, which is obscurely divided into two joints, 

 and gives off at its extremity two long branches, beauti- 

 fully fringed, with transparent and delicately plumose 

 cilia ; while a third shorter branch, equally plumose, 

 arises from the base of the two preceding, and is curved 

 backwards and inwards. The fourth pair (t. XXXI, f. /?-,/) 



