WOODWARD : ANATOMY OF NATALINA CAFFRA. 273 



The postero-cTorsal longitudinal muscle is enormously developed 

 {d.L, Fig. 5), and is broken up into a large series of distinct muscles 

 arising from all parts of the radula and radula-sac above and behind 

 the odontophoral cartilage. These muscles run oblifiuely backwards, 

 and are inserted upon the edges and inner surface of the odontophoral 

 cartilage. Posteriorly we find a more compact portion of this muscle, 

 which arises from the under side of the radula and runs back to 

 the extreme posterior end of the odontophoral cartilage. These 

 muscles are the ones upon which the greatest amount of work falls, 

 i.e. the pulling in of the radula after the teeth have been inserted 

 in the flesh of the victim, the whole rasping action of the radula 

 depending on the size of the teeth and the power of these retractor 

 muscles. 



The odontophoral cartilage has lost all its cartilaginous nature, its 

 muscular elements alone remaining ; it is here a long scoop-shaped 

 mass of muscular tissue, whose fibres are extremely short and arranged 

 vertically to the surface of the scoop. Besides giving support to the 

 radula and attachment to its muscles, it is itself an important motor of 

 that structure, the contraction of its fibres acting in the same way 

 as the intrinsic muscles of the human tongue, and producing an 

 elongation of this structure and a consequent protrusion of the radula. 

 A mass of longitudinal muscular fibres is attached to the free edge 

 of the odontophoral cartilage on either side near the anterior end ; this 

 mass probably bends up the free end of the scoop, and so assists the 

 rasping action of the radula {l.o.m., Fig. 6) : it is, like the preceding, 

 an intrinsic muscle. The extrinsic muscle of the cartilage consists 

 of a series of adjuster muscles (Figs. 6 and 7 o.a.). 



The radula has been fully described by Pilsbry. The radula-sac is 

 very long, running through the buccal mass in the dorsal groove of 

 the odontophoral cartilage, close to which it lies anteriorly, but 

 posteriorly it becomes buried up in the great retractor muscle of 

 the radula, eventually appearing on the dorsal surface of the buccal 

 mass near its posterior end, which, however, it does not quite reach. 

 The retractors (r.m., Fig. 4) of the buccal mass arc attached to the 

 sides and dorsum of that structure near its posterior end, and pass into 

 the great columella muscle. A numerous series of protractors, etc., 

 pass from its anterior end to the cephalic wall round the mouth 

 (Fig. 4). 



The combined action of these muscles may be explained in the 

 following manner : — The odontophore would be protruded by the con- 

 traction of the transverse vertical fibres of the odontophoral cartilage, 

 assisted by the great sphincter muscles of the buccal mass ; these latter 

 would further serve to press the tongue firmly against the flesh of the 

 prey ; a contraction of the antero- ventral longitudinal muscles would 

 then pull the radula forward, the convex smooth anterior surface of 

 the teeth gliding over the food till the teeth were fully .erected ; this 

 would be followed by a contraction of the levator muscles of the 

 front of the odontophore, both intrinsic and extrinsic, thus lifting up 

 the scoop and driving the teeth into the flesh, accompanied almost 

 simultaneously by a contraction of the great pbstero-dorsal longitudinal 



