194 PLEUROBRANCHUS. 



slight furrow which runs obliquely from back to front ; color pale 

 reddish-brown or tawny, rarely milk-white ; spire extremely small 

 but distinct, twisted sideways, and placed at a short distance from 

 the inner margin at the posterior or smaller end ; it consists of two 

 whorls, the first of which is tubercular and somewhat prominent ; 

 mouth open throughout ; dorsal margin gently curved, flat, slightly 

 reflected and thickened ; inner margin short ; ventral margin long 

 and nearly straight. Length '6, breadth '325 inch. (Jeffreys}. 



English and Irish Coasts, under stones at low water, sometimes 

 deeper ; Norway ; the Channel, and Ocean Coast of France. 



Bullaplumula MONT., Test. Brit., i, p. 214, pi. 15, f. 9, and vign. 

 2, f. 5 (1803). Pleurobranchus plumula FORBES & HANLEY, Hist. 

 Br. Moll., iii, p. 559, pi. 114F, f. 6, 7 ; pi. xx, f. 1, 2. JEFFREYS, 

 Brit. Conch., v, p. 11, pi. 1, f. 2. SOWERBY, Conch. Icon., xvii, f. 1. 

 SARS, Moll. Reg. Arct. Norv., p. 363, pi. xiii, f. 1 (jaws and den- 

 tition). P. sideralis LOVEN, teste Jeffreys. Berthella porosa Leach, 

 BLAINVILLE, Diet. Sci. Nat, xxxxi, p. 370 (1826); Man. de 

 Malac., p. 470, pi. 43, f. 1. Pleurobranchus plumulatus Mont., 

 LOCARD, Prodr. Mai. Fr., in Ann. Soc. d'Agric. Lyon (5), viii, 

 1885, p. 69 (1886). PL fleuriami D'ORBIGNY, Voy. dans 1'Amer. 

 Merid., p. 205, foot-note. Cleantus montagui LEACH, Synops. Moll. 

 Gt. Brit., 1852, p. 28. 



This species is type of Berthella Blainv. It differs from the 

 Mediterranean form (stellatus) in having the plates of the jaws 

 finely denticulate (pi. 74, fig. 1), and the lateral teeth smooth (pi. 

 74, figs. 2, 3). There are also more branches on the gill, and the 

 shell is apparently more quadrate. 



A variety alba Marshall (Journ. of Conch., Leeds, vii, p. 265) 

 has been proposed for specimens from Jersey with the shell pure 

 white. Fifty per cent, from that locality are stated to be white. 



P. STELLATUS Risso. PI. 52, figs. 62, 63 ; pi. 74, figs. 95, 96. 



Body oblong, ovoid, the teguments of very delicate consistence, 

 general color transparent yellow. Mantle thick, very large, more 

 vividly colored than the rest of the animal, and very slightly emar- 

 ginate in front ; under a strong lens showing a multitude of dots of 

 deeper color. Foot small, oval, and wholly covered by the mantle. 

 Gill pinnate, folded longitudinally, composed of 15 pinnules on 

 each side of the rachis. Orifices of genitalia united in a sort of 

 cloaca, and placed in front of the insertion of the gill. Anus behind 

 gill-insertion. Length 29, width 20 mill. 



