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Siphono-pallial articulation This is very vreak in 



Eledone, as in all Octopoda. It consists of two shallow 

 ridges on the postero-ventral edge of the funnel, which 

 fit in two corresponding shallow grooves of the anterior 

 ;ind inner ventral surface ol the mantle (PL II, fig. 0^, 

 l.f.r., I.m. (/v.). 



Vertical muscular septum.— This consists of two 

 symmetrical triangular sheets of muscle, which run out 

 from the mantle to the body and enclose the anus between 

 their anterior edges (PI. II, fig. 8; PI. Ill, fig. 11, m.s. } 

 m 1 s 1 and an.). The septum is covered by the general 

 epithelium of the mantle cavity. The shortest side of 

 each sheet is anterior, while the longest runs from the 

 base of the mantle out obliquely to the visceral mass. 

 The vertical line of attachment of the septum extends 

 from the ventral posterior extremity of the mantle to 

 within half an inch of its anterior edge (figs. 8 and 11, 

 m.s.a.). By referring to fig. 11 it will be seen that after 

 the septum enters the mantle cavity (on.), it is free for 

 some distance from the visceral mass, and hence adheres 

 only to the mantle. About half-way up the length of the 

 oviduct, it becomes attached to the visceral mass. Hence 

 there is free communication, posteriorly, between the 

 right and left halves of the mantle cavity (fig 11, P.C.). 

 Each of the two halves of the septum consists of two 

 rather thin sheets of muscle (1) an upper- sheet sloping 

 from the mantle, obliquely inwards and downwards, to 

 the body (tigs. 8 and 11, ///,'): and (2) a lower sheet sloping 

 from the mantle, obliquely inwards and upwards, l<> the 

 body i figs. 8 and 11, m.p.). 



The lower strands of the upper sheet and the outer 

 strands of the lower sheet run towards one another, and 

 form a superficial sheet which runs along with the funnel 

 retractor muscle, down to the mantle (fig. 11, ///./., 



