. Bulletin of the Natural History Museum Zoology. FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS 59. Fig. 4 Radulae of Crassispirinae. a. Crassispira (Crassispira) incrassata b. Crassispira (Crassispira) maura c, Crassispira (Gibbaspira) dysoni d, C. (Glossispira) harfordiana flucki. Scale bars = 20|jm. walls are equally developed along its is a small anterior buccal tube sphincter, positioned at the base of the small sac-like enlargement of the buccal tube, which also has an epithelial pad. An intermediate buccal tube sphincter is absent. The buccal tube is very narrow, both inside
. Bulletin of the Natural History Museum Zoology. FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS 59. Fig. 4 Radulae of Crassispirinae. a. Crassispira (Crassispira) incrassata b. Crassispira (Crassispira) maura c, Crassispira (Gibbaspira) dysoni d, C. (Glossispira) harfordiana flucki. Scale bars = 20|jm. walls are equally developed along its is a small anterior buccal tube sphincter, positioned at the base of the small sac-like enlargement of the buccal tube, which also has an epithelial pad. An intermediate buccal tube sphincter is absent. The buccal tube is very narrow, both inside the proboscis and for some distance behind it, and lined with a very low epithelium. Some distance behind the proboscis, the buccal tube expands greatly and forms two small, poorly-muscularized lips which are directed anteriorly, similar to the 'valvule.' (Sheridan et al. 1973). The buccal lips are large and muscular, with the dorsal one inverted inside the buccal cavity. Buccal mass and oesophagus The buccal mass is medium-sized and situated to the posterior of the proboscis base. Its dorsal wall is very thin. By contrast, the ventral wall near the entrance of the radular diverticulum is thick, but formed mainly by a layer of loose connective tissue, which is 4-8 times thicker than the muscle layer. The oesophagus is greatly elongated between the buccal mass and nerve ring, forming a long loop. The buccal sac is of medium length and narrow. Glands The salivary glands are very large and acinous, with ducts that are thick and coiled, but become very thin as they approach the buccal venom gland changes in histology after passing anteriorly through the nerve ring. The duct of the gland is narrow, unciliated, and opens just to the posterior of the buccal cavity. The muscular bulb is large, with most of the wall formed by two subequal layers of longitudinal muscle fibres, divided by a connective tissue layer, with a third innermost, thin layer of circular muscle fibres. Odo
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