PATELLA. 225 



fcer a swerve to the left, bends back along* about two- 

 diirds of the under surface of the visceral mass in the 

 median plane. It then -curves well round to tiie right 

 side, taking a forward course to about the middle of the 

 visceral mass, after which it bends sharply upon itself 

 arid retraverses the greater part of its former course. 

 This second part is closely applied to the right side of 

 the first, and its caecal tip extends forwards almost as 

 far as the back of the cushion. The anterior part, at 

 least, of the radular sac and the odontophore, are sur- 

 rounded by a large blood space, whence blood travels 

 both to the visceral hump and to the foot. 



The Radula is altogether about twice the length of the 

 animal, and is a narrow belt-like structure with rows 

 of teeth, having at its anterior end a flat plate-like ex- 

 pansion on either side. This plate is bent over the front 

 end of the cushion where the covering epithelium has 

 secreted it. Behind this the radula sinks into a groove along 

 the middle of the odontophore and runs back into its sheath. 

 The teeth of the radula are arranged in convexly curved 

 transverse rows, the convexity being forwards on the dorsal 

 surface of the cushion. There are twelve members to 

 each row (fig. 14). Of these twelve the four central ones 

 are similar, although the middle two are slightly smaller 

 than the others. Each consists of a yellow stalk and a 

 black-tipped brown " claw," the claw having its concavity 

 directed backwards. Next to these four and behind their 

 level is another tooth of the same kind but larger and 

 with three claws. Lateral to these again we have three 

 pairs of teeth without claws, these have their ends curved 

 slightly backwards. They are at the same level as the 

 four central teeth. 



. The absence of one definitely differentiated median 

 tooth characterises all the Docoglossa except i)\e Lepetida), 

 T 



