80 ANNELIDES. 



and two or more kinds are often found coexistent on the same foot. 

 The forms may, perhaps, be reduced to the following : — 



Capillary. — Slender, flexile and hair-like, as e.g. the coloured 

 hairs of Aphrodita aculeata. 



Setaceous, slender and tapered insensibly from the root to a sharp 

 point (PI. III. figs. 6, 7). 



Lanceolate, straight on the lower half, bulged about the middle, 

 whence it tapers to a point sharp on both sides (figs. 10, 11, 13, 14). 



Ventricose. — When the shaft is enlarged on one side (figs. 8, 9). 



Tarsiform. — A stout bristle terminating in a point curved and 

 sharp like a claw (figs. 17, 18, 19). This is common in the Aphro- 

 ditacese. It is somewhat grooved and denticulate on one side. 



Spinous. — A stout bristle resembling the spine or spinet, but 

 distinguished by being fasciculate (figs. 21, 22). It is more or less 

 flexuose or bent like the letter/ (fig. 23) in many subcephalous anne- 

 lids ; and is dark-coloured and straight in Aphrodita aculeata. 



The compound Bristle is peculiar to the " Annelida rapacia." It 

 is a bristle of which the shaft is broken into two halves by an imper- 

 fect sort of joint. The lower portion is the shaft, and the upper the 

 terminal piece. (See PI. IV.) 



The intermediate joint may be simply oblique with the edges 

 approximate (PI. IV. fig. 1), or separate (figs. 4, 5), or with the 

 shaft and terminal piece attached merely by a point (fig. 11). Or 

 the two pieces may be connected by a mortise joint (fig. 7), or by a 

 variously formed socket (figs. 2, 9, 13). 



The shaft is usually straight, smooth or serrulate, and a little 

 enlarged towards the outer end. The terminal piece varies in shape 

 like the simple bristle. It is acicular when it is straight and slender, 

 and tapers to a very sharp point (PI. IV. fig. 7). 



Tarsiform. — When it is elongated and slightly bent, and brought 

 to a point, like the hind claw of a small bird (PI. IV. fig. 1). 



Falcate. — When the piece is short, and curved at the apex so as 

 to resemble the mandible of a small bird (PI. IV. figs. 2, 6, 12). 



The British species are divided into the following Tribes : — 



Tribe I. Bapacia. Animal-killers. 



Body with soft appendages, generally disposed on the whole 



length of the body. Feet distinct, armed with setse, which are 



sometimes hooked. Head generally distinct, provided with eyes, 



antennae, a retractile proboscis, and often with jaws. Living on 

 marine animals. 



Tribe II. Limivora. Mud- eaters. 

 Body with the soft appendages collected together at the cephalic 

 extremity. Feet of two kinds, generally deprived of cirrhi, and 

 armed with hooked bristles. Head not distinct, without eye- ten- 

 tacles. Protractile proboscis or jaws. Eating mud and the dead 

 animals and vesicles it contains. 



