ORDER NUDIBRANCHIATA. 39 
furrow, which enables it to clasp the stems of the fuci; no 
veil; the mouth resembling a little proboscis ; orifices as in 
thethys; the compressed tentacula terminated by a cavity, 
from which issues a little uneven point; two pairs of mem- 
branous crests on the back, bearing on their internal surface 
pencils of filaments, which are the gills. ‘The middle of the 
stomach is invested with a fleshy ring, internally armed with 
horny and trenchant lamine like knives. 
S. Pelagica, L., Cuv. Ann. du Mus. VI. Ixi. 1. 3. 4: com- 
mon on the floating fucus of almost every sea. 
GLAUCUS, Forster. 
Body elongated; orifices of the anus, and of the genital 
organs, as in the preceding ; four very small conical tentacula ; 
and on each side three gills, each of which is formed of long 
slips, arranged like the sticks of a fan, which also aid them in 
swimming. These are the beautiful little animals that inhabit 
the Mediterranean and the Atlantic, prettily coloured with blue 
and mother-of-pearl. They swim on their back with great 
swiftness. ‘Their anatomical structure is very similar to that 
of the tritonia; but the species are not yet well ascertained. 
(Doris radiata, Gm., &c.) 
LANIOGERUS, Blainv. 
Two series, on each side, of small and finely-pectinated 
lamine, which are the gills; the body, shorter and thicker 
than that of a glaucus; but there are four small similar tenta- 
cula. (Laniogerus Elfortii, Blainv. Malac. pl. xlvi. f. 4.) 
Eo.iptia, Cuv., 
Resembles a small limax in form: four tantacula above and 
two on the sides of the mouth ; the gills, composed of lamine, 
arranged like scales, more or less crowded, on each side of the 
back. Found in every sea. (Doris papillosa, Zool. Dan., &c.) 
