ON THE BRITISH ANNELIDA. 217 



trating the adjacent soil. To the genus Cirrhatulus^ through the author's re- 

 searches, several new species have lately been added. Here the setae assume 

 the shape of elastic tape, ending in a fine point, affecting on each segment 

 a lateral situation. The lateral cirri are shorter and less numerous. 



In Aphrodita aculeaia, it is not difficult to discover every locomotive ap- 

 pliance required to move with facility through semi-fluid sand. The feet 

 form thirty-two pairs in number ; the anterior and posterior are minute, but 

 they gradually increase in size towards the middle of the body, where they 

 attain their greatest development. They are of two kinds; the squamiferous 

 and cirrigerous, both varieties being divisible into two branches — a ventral 

 and a dorsal. The ventral branch or proper foot forms a stout rough tuber- 

 culated conoid process, armed with a stout spine protruded from the pale 

 papillary apex, and with four or five firm bristles proceeding 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 a tooth-like process on the inner side beneath this 

 point. 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 

 progression along the ground; that of the squamous feet is armed with two 

 bundles of bristles, arranged in a fan-shaped manner : they are compara- 

 tively short, curved like the italic letter/, and roughened with minute gra- 

 nulations on the upper half; the bristles of the other brush, placed between 

 the dorsal 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 

 Islander. The notches are not opposite, but alternate, and they are enclosed 

 within a plain sheath, consisting of two dilated valves which shut upon them. 

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

 bristles are simple and curved like those of the dorsal fascicles of the squa- 

 mous 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. This worm is generally an occupant of deep water. It crawls 

 along the muddy bottom at a few fathoms below the surface. In motion on 

 a hard surface its feet present an extremely interesting spectacle. It gives 

 pleasure to watch the precision with which they are unsheathed, and the 

 regularity and order with which each foot succeeds another in the slow and 

 snail-like march. 



Polynoe are always found on the under surfaces of stones, over which they 

 are capable of creeping with considerable freedom. Their swimming capa- 

 city is very inferior — sinking soon to the bottom to crawl along. In relation 

 to the Polynoe generically it may be stated, that the feet are bifid, the supe- 

 rior branch being small and almost confluent with the inferior, which is 

 greatly developed ; that the superior cirri are long and the inferior short and 

 conical ; that the bristles of the superior branch are short and always slenderer 

 than those of the inferior, subulate and smooth at the point, or like the infe- 

 rior bristles, somewhat thickened and serrulate along the edge. The spines 

 present no peculiarity. The first pair of feet are destitute of bristles, but 

 are terminated by two long tentacular cirri, which advance on each side of 

 the head and resemble antennae ; while on the last segment we find filiform 



