29 1 Dr. Johnston on the British Nereides. 



Plate VI. fig. 1. Nereis pelagica, of the natural size; 1 a. The head and 

 prohoscis magnified ; 1 b. A lateral view of one of the feet; 1 c. Two bris- 

 tles. Fig. 2. The young ? of Nereis pelagica. 



2. N. margaritacea, of a uniform mother-of-pearl colour, 

 post-occipital segment equal in breadth to the two following ; 

 jaws with five or six serratures, the apex plain ; superior cirrus 

 elongate, the inferior lobed at the base ; bristles numerous, 

 the dorsal brush with two, and the ventral with four spines. 

 Plate VI. fig. 3. 



Nereis margaritacea, Leach in Supp. Encyclop. Brit. i. 451. pi. 26. Au- 



douin and M. Edwards in Ann. des Sc. Nat. xxviii. 217. Wilson in 



Encyclop. Brit, {last edit.) xi. 220. — N. margarita, Montagu in Lin. 



Trans, vii. 82. Tnrt. Brit. Faun. 135. — Lycoris margaritacea, Lam. 



Anim. s. Vert. v. 312. seconde edit. v. 550. Stark, Elem. ii. 139. 



Hob. Amongst the rocks at Milton, rare, Montagu. Coast of Berwickshire, 



also rare. Mr. Wilson informs us that " this species is common near the 



Bell Rock, and is subject to great variation of colour," but the latter remark 



probably flows from a confounding of more than one species together. 



Desc. Body, about four inches long, vermiform, rounded 

 dorsally and flattened on the belly, of a uniform mother-of- 

 pearl colour, iridescent, the feet tinted with a dusky pale green. 

 Head corneous, brown, sub quadrangular : eyes four, very di- 

 stinct, occipital, blackish : antenna and palpi similar to those 

 of JV. pelagica, nor is there any material difference in the pro- 

 boscis, but the jaws are armed with only five or six denticu- 

 lations, and the point is longer and smooth : tentacular cirri 

 subequal, reaching to the posterior margin of the post-occi- 

 pital segment, which is twice as broad as the following : seg- 

 ments rather narrow ; the anterior with small feet, which be- 

 come gradually larger as we reckon backwards, attaining their 

 maximum of development behind the middle, whence they 

 again lessen : superior cirrus longer than the branchial ? lo- 

 bules ; the inferior cirrus of the anterior feet simple, that of 

 the more developed feet with a lobe and short filament at its 

 base : bristles in two considerable brushes, colourless, jointed, 

 the terminal piece long and setaceous ; spines conical, corneous, 

 some darker than others. 



Plate VI. fig. 3 a. The head of Nereis margaritacea, with the proboscis 

 protruded; 3 b. A jaw separated and highly magnified; 3 c. An anterior 

 foot (from the twelfth segment) ; 3 d. A foot from near the middle of the 

 body, viewed laterally. 



