306 Dr. Johnston on the Irish Annelides. 



crease in size towards the middle of the body, where they at- 

 tain their greatest development. They are of two kinds, — 

 the squamiferous and cirrigerous, — but a foot of either is di- 

 visible into two branches, viz. a ventral and dorsal. The ven- 

 tral branch (or proper foot) forms a stout rough tuberculated 

 conoid process armed with a stout spine protruded from the 

 pale papillary apex, and with four or five firm bristles proceed- 

 ing from under the apex and partially surrounding the spine. 

 The spine tapers insensibly to an obtuse point, is smooth, 

 and of a pale yellow colour : the bristles are of a rich 

 burnished brown colour, with a round shank which grows 

 a little thicker upwards, and is terminated with a curved 

 cutting point like a pruning-knife ; in most of them there is 

 also a tooth-like process on the inner side beneath this point. 

 (Plate V. fig. a.) The cirrus of the foot does not reach its apex, 

 excepting that of the first pairs ; it is fleshy, setaceous, and 

 of a pale colour. The dorsal branch of all the feet has an 

 upward direction, and cannot be used as an organ of pro- 

 gression along the ground : that of the squamous feet is 

 armed with two bundles of bristles {b), each proceeding from 

 a distinct tubercle ; the innermost or dorsad brush consists of 

 many slender golden yellow bristles, arranged in a fan-shaped 

 manner ; they are comparatively short, curved like the italic 

 letter f, and roughened with minute granulations on their 

 upper half (c) : the bristles of the other brush, placed between 

 the dorsad one and the proper foot, are remarkable for their 

 stoutness and length ; they are of a rich dark brown colour, 

 straight, and terminated with a lanceolate point, which is 

 notched on, each side with four reverted barbs, so that the 

 bristle resembles the barbed arrow or spear of the South-sea 

 islanders [d). The notches are not opposite, but alternate, 

 and they are inclosed within a plain sheath, consisting of two 

 dilated valves which shut upon them [e). The cirrigerous foot 

 has a single fan-shaped brush of bristles only ; the bristles 

 are simple and curved like those of the dorsad fascicles of the 

 squamous feet, but they are more numerous, slenderer, longer, 

 of a paler colour, and quite smooth; they are unequal in 

 length, some of them very fine and hair-like, and the whole 

 brush is usually matted and soiled with extraneous matters. 

 Length of the worm 2 inches ; breadth y^^jths. 



