3i6 



POLYCHAETA 



of the various processes of the head, of the lobes of the feet, the 

 arrangement of the " paragnaths " (see Tig. 125, d), and so forth. 

 The general features of the family have been already described. 

 The genus Nereis is represented by six fairly common species 

 on our coast, which are almost world-wide in distribution. 



N. diversicolor Miill. is about 3 to 4 inches in length, of a 

 general fleshy-red colour, though tending in some cases to yellowish- 

 brown or even greenish. It may be distinguished by two diverging 

 brown bands, which start on the peristomium and pass backward 

 one along each side of the body for several segments. The pro- 

 stomium is broader than it is long. The worm burrows in mud 

 or sand, all round our coast between tide-marks. It has a very 

 wide distribution, being met with on this side of the Atlantic, and 

 off the coast of Greenland, and off Japan. It is even found in 

 brackish water at Bembridge, Isle of Wight. 



N. cultrifera Gr. is green or greenish-grey, with a series of 

 small rectangular light spots along the 

 mid-dorsal surface, and oblique light lines 

 at the sides of each segment. Posteriorly 

 the greenish pigment becomes less and 

 less till the hinder segments are flesh- 

 coloured. The prostomium is as long as 

 it is broad. This species attains a length 

 of 6 inches. Southern coasts : locally 

 known as " Red Cat." 



JY. dumerilii Aud. and Edw. is rather 

 smaller and narrower than the two preced- 

 ing species ; it is reddish-violet in colour, 

 marked with darker transverse lines in 

 each segment. It is readily recognised by the two dark brown 

 spots on the upper surface of the base of the notopodium in most 

 of the segments, and by the great length of the peristomial cirri, 



Fig. 168. Nereis cultrifera 

 Gr. x 6. Head with buccal 

 region everted, to show the 

 arrangement of the jaws. 

 (From Ehlers.) Cf. N. 

 diversicolor, Fig. 125, p. 

 248. 



the 



longest 



of which reaches the fifteenth segment. It is some- 



times found enclosed in a cocoon-like tube of hardened grey 

 mucus, more or less covered with foreign particles, such as sand 

 grains. Atlantic, Mediterranean, Japan. 



JV. pelagica L. is red -brown or bronze in colour, and is 

 generally larger than the other species, from which it is dis- 

 tinguished by being widest about the middle of the body (see 

 Fig. 122, p. 246); whilst in the preceding species the greatest 



