204 THE CEPHALOPODA 
It follows that in all living Cephalopods except Nautilus the 
shell is localised on the anterior or physiologically dorsal side of 
the body, and is enclosed by the mantle, which therefore appears 
to be a naked, bell-shaped sac (Figs. 252, 254, 287, etc.). The 
whole circumference of the mantle border is free in the Decapoda 
(Fig. 259), with the exception of Sepiola, in which it is fused to the 
head anteriorly in the middle line. Similarly, in the Octopoda, the 
border of the mantle is fused to the head anteriorly and laterally, 
whereby the pallial aperture is much reduced, especially in Cirrho- 
teuthis (Fig. 260) and Opisthoteu- 
this (Fig. 300). 
In the Decapoda a more secure 
union between the mantle and 
the funnel, during the expulsion 
of the water used in respiration 
Fic. 259. 
Ctenopteryx cyprinoides, ventral aspect. Fic. 260. 
a, arms; e, eye; fi, fins; fw, funnel with 
valve; ol, olfactory organ or rhinophore ; Cirrhoteuthis meangensis, Hoyle (young speci- 
so, socket of the funnel; te, tentacular men), ventral aspect. ji, fin; fu, funnel; m, 
arms. (After Joubin.) mouth. (After Hoyle.) 
through the latter structure, is ensured by the following mechanism : 
the free borders of the mantle bear on each side a cartilaginous pro- 
jection (Fig. 272, c’) which fits into a corresponding depression in 
the funnel (Figs. 272, ¢; 259, so), the whole constituting the so- 
called ‘resisting apparatus ” of foreign authors. In certain Oigopsida 
of the family Cranchiidae (Cranchia, Leachia) and in the Octopoda 
this apparatus is but feebly developed, and in Cirrhoteuthis, where 
it would be useless, it has disappeared. Otherwise the funnel is 
quite independent of the mantle: it is only in Amphitretus among 
the Cirrhoteuthidae that the mantle border is united to the 
funnel by a ventral suture, leaving an opening into the pallial 
cavity on either side. Similarly, in Grimalditeuthis and Symplecto- 
