234 MARTIN F. WOODWAED. 



acting directly upon it, or upon tlie inf ra-radular membrane ; 

 and those concerned in the movements of the odontophoral 

 cartilages. 



On examination of the odontophore from the side, after 

 removal of the extrinsic muscles, three muscles will be seen 

 (fig. 30 B). One of these {d. l.m.) runs from the outer edge 

 of the infra-radular membrane to the upper border of the 

 main odontophoral cartilage, the fibres being arranged some- 

 what obliquely to the length of the cartilage. This muscle 

 must by its contraction serve to flatten, i. e. expand, the 

 radula, and at the same time slightly pulls it back over the 

 odontophoral cartilages. It is the largest and most powerful 

 of the intrinsic muscles, and may be termed the dorsal or 

 postero-dorsal longitudinal muscle. Three muscles are an- 

 tagonistic to this; one of these {v. l.m.) is a small ventro- 

 lateral band attached iu front to the antero-ventral edge of 

 the infra-radular membrane, and behind to the accessory 

 basal odontophoral caitilage. This muscle, which we may 

 term the ventral or antero-ventral longitudinal muscle, serves 

 to pull the radula over the odontophoral cartilage, and also 

 to flatten the anterior part of the radula. The second of 

 these muscles is not seen in this dissection, since it lies on the 

 inner side of the main cartilage; it is, however, shown in the 

 median, the ventral and dorsal aspects (fig. 30 E, F, G, i. I. m.) . 

 This muscle is attached to the under side of the radula and 

 to the infra-radular membrane, where it underlies the middle 

 functional part of the radula, its insertion forming an oblique 

 line, starting near the median ventral line, and passing up- 

 wards and outward until it ends on the edge of the basal 

 membrane of the radula ; posteriorly this muscle is attached 

 behind to the accessory basal cartilage. The contraction 

 of this muscle causes the radula to assume once more its 

 V-shaped grooved character, and iu addition it acts as a 

 powerful retractor. It may be termed the internal longi- 

 tudinal muscle. The third muscle is a very small one (fig. 

 30 D, X.) attached to the infra-radular membrane laterally, 

 and running forwards it is inserted up the anterior portion 



