263 
stem, on which are set a great number of transverse plates, 
in such a manner that the axis of the stem passes througli 
the centre of the plates. The anterior and lateral regions of 
the hood are completed by two narrower processes, each of 
which contains a similar tentacle, and the lateral portions 
of the sheath are formed by sixteen or seventeen smaller ten- 
taculiferous processes, the surfaces of which are more or less 
distinctly annulated. When the sheath is opened out, there is 
seen to be attached to its inner surface, on each"side, close to 
the re-entering angle between it and the lip which surrounds 
the beak, and along the line of junction of the lateral part of 
the sheath with the isthmus, a thin, free quadrate lobe, which 
carries twelve tentacles. The isthmus joins the posterior 
edges of these outer tentaculiferous lobes, as well as those of 
the two halves of the sheath, and it exhibits on its anterior, 
or inner surface, a broad area beset with delicate, close-set, 
curved laminae. Two other similar, but much thicker, 
inner tentaculiferous lobes, which also carry twelve ten- 
tacles, lie between these and the lip. They are quite free 
from the outer tentaculiferous lobes, and unite with the 
sheath only above and behind. Like the halves of the 
sheath, these two lobes are united behind by a thick isth- 
mus, the suiface of which presents a number of parallel 
longitudinal laminae. The beak, wliich is hidden by the 
sheath and the lobes, is surrounded by the thin circular lip 
already mentioned, the free margin of which is papillose. 
Besides these, there is a short, conical tentaculiferous process 
above the pedunculate eye, and another below it." The 
Cuttle Fish and their allies (Dihranchiata), have fewer 
arms, the number being eight in the Odopoda, to which 
group the genera Octopus and Eledone are referred ; whilst 
in the Decapoda, wliich includes, amongst other genera, 
Sepia, Sepiola, Loligo, and Rossia, tliere are two additional 
arms, which are elongate and club-shaped at their extremi- 
