232 MARTIN F. WOODWARD. 



are, however, less developed posteriorly where the salivary 

 gland (fig. 8, si. g.) occupies the roof of this structure. 



On opening the buccal cavity a couple of laterally placed 

 folds, covered with horny matter, will be seen (fig. 9,;'.). 

 These folds, which undoubtedly correspond to the jaws of 

 other Gastropods, are but feebly developed in Pleuroto- 

 maria, and probably serve, as Dall suggested, to protect 

 the soft wall of the buccal cavity from the scraping action of 

 the radula. The structure of one of these is shown in fig. 

 54. In front of the horny jaws a number of small flattened 

 papillae, also covered with horny matter, are to be seen (fig. 9, 

 h. p.). Between and behind the jaws the veutrally placed 

 odontophore may be seen bearing the chitinous radula {rd.), 

 the functional portion of which when at rest appears some- 

 what V-shaped when viewed from above, and thus only covers 

 the central portion of the odontophore, the sides of which are 

 covered by the lateral extension of the radular membrane. 

 Thus the whole of the buccal cavity is more or less protected 

 by a lining of chitin. 



The Salivary Glands form a compact mass in the roof 

 of the alimentary canal, at the junction of the buccal mass 

 and the crop (figs. 6 — 8, s. g.) ; their ducts {si. d.), which are 

 closely related to the buccal nerves, run forward within the 

 thickness of the wall of the buccal mass, and open into the 

 buccal cavity just above the odontophore (fig. 10). The 

 gland, which is a much branched oue (fig. 8), was not well 

 enough preserved to enable me to study its histology. 



The odontophore is enormously developed, being highly 

 muscular, and further strengthened by the odontophoral car- 

 tilages. When at rest it forms a comparatively slight projec- 

 tion into the buccal cavity, but, on the other hand, it projects 

 as a great muscular mass into the hgemocoele (fig. 7, od.). 

 Between it and the crop the enormous radular sac (r. s.) will 

 be seen extending back for two or more inches, and becoming 

 involved in the anterior lobe of the right kidney. 



The Musculature of the Buccal Mass. — As in other 

 Odontophora, the muscles of the buccal mass can be divided 



