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. 
Bulla plumula Mont., Test. Brit., i, p. 214, pl. 15, f. 9, and vign, 
2, f. 5 (1803).— Pleurobranchus plumula Forpes & Han ey, Hist. 
Br. Moll., iii, p. 559, pl. 1148, f. 6, 7; pl. xx, f. 1, 2—JEFFREYs, 
Brit. Conch., v, p. 11, pl. 1, f. 2—SoweErsy, Conch. Icon., xvii, f.1. 
—Sars, Moll. Reg. Arct. Norv., p. 363, pl. xiii, f. 1 (jaws and den- 
tition).—P. sideralis LovEn, teste Jeffreys.— Berthella porosa Leach, 
BLAINVILLE, Dict. Sci. Nat., xxxxi, p. 370 (1826); Man. de 
Malac., p. 470, pl. 48, f. 1.—Pleurobranchus plumulatus Mont., 
Locarp, Prodr. Mal. Fr., in Ann. Soc. d’Agrie. Lyon (5), viii, 
1885, p. 69 (1886).—PIl. fleuriausi D’ORBIGNY, Voy. dans lAmeér. 
Mérid., p. 205, foot-note.— Cleantus montagui Leacu, Synops. Moll. 
Gt. Brit., 1852, p. 28. 
This species is type of Berthella Blainv. It differs from the 
Mediterranean form (sted/atus) in haying the plates of the jaws 
finely denticulate (pl. 74, fig. 1), and the lateral teeth smooth (pl. 
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; pl.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. 
