No. 478] ODONTOPHORAL APPARATUS IN SYCOTYPUS 727 



not in the living animal. The looseness of the membrane thus 

 allows of the forward and backward play of the ribbon in rasping. 

 The nuiscles that are responsible for the rasping movements of the 

 ribbon are not atiached to the ribbon directly, but to fhr innuhraiie 

 to which the ribbon is adherent (the ra( hilar inciiibniiu' i. Bv 

 treatment with alcohol the ribbon is reathly scpnraKd from its 

 membrane. That part of the ribbon wiiich is mature and in 

 use is from three to four cm. long, whereas th(> inunature part 

 which is folded up within the rathdar sac, and which caiuiot be 

 drawn out over the rim of the cartilage head is some five cm. long. 



It is to the radular sac that the large retractors of the nl>l)on 

 are attached, the protractors being attached to the ventral pouch 

 of the radular membrane (Fig. 12, prs., ogr.). 



Retractors and Protractors of Radi i.a; ('kutain .\( ( i.s- 

 soRY Mi\scLEs — Their Xkiu j; Si i'i>i.v 



Retractors (together with Certain AceexHorij J/y/.sr/r.v). — The 

 retractors of the lingiud ribbon are, as above stated, inserted by 

 tendons into the ra(hilar sac. At the region of their insertion they 



four separate roots ciui be distinguished (Figs. !t, II. 14!: 



halves, j)asses l);ick to be inscnc<l on either side into the hueral 



base of the proboscis. 



side and are inserted h\ a half dozen bundles into the lateial wall 

 of the proboscis .somewhat anteriorly to the iiixM-tion of the median 



