494 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
other Decapods, and this means of locking the mantle 
seems to have weakened as the dorsal fusion formed, and 
so rendered it less necessary. Also, as Eledone is a much 
less powerful swimmer than the Decapods, the need of a 
strong funnel articulation is lessened. The funnel cavity 
is three-chambered. The central largest chamber alone 
opens to the exterior, while the lateral chambers are blind 
anteriorly. All three, however, open into the mantle 
cavity. The central chamber is cut off laterally from the 
side chambers by the great depressor or retractor muscle 
of the funnel. This forms the ventral and ventro-lateral 
wall of its own side of the funnel, and then runs out to 
its insertion on the anterior border of the mantle cartilage 
of its side. Two other pairs of muscular bands, which 
are narrow and rather short, run in from the dorsal 
surface of the funnel to the cephalopedal mass. They 
act as protractors of the funnel, and are exposed by — 
cutting through the skin behind the funnel, as in PI. II, 
fig. 9, sk., and turning the funnel ventrally. The 
protractors form a letter W, the external pair being 
inserted above the inner pair, on the funnel wall. The 
external pair run outwards and dorsally, to join in with 
the capito-pedal muscles just below the eyes. The 
internal pair run inwards to the ventral surface of the 
cranial cartilage, and are attached there. The dorsal wall 
of the funnel is formed by a broad pair of muscles which 
then run outwards from the posterior lateral region of the 
funnel to the top of the mantle. Thus with the depressor, 
these two nuchal or collar muscles bound the lateral 
funnel chamber. Hence the funnel muscles are arranged 
in three sets: — 
(a) One pair of depressors (fig. 9a,, L’.).), 
(b) One pair of nuchal muscles (fig. 9, codl.), and 
(c) Two pairs‘of protractors (fig. 9, L.F.Pr., L.F.Pr;). 
