. Bulletin of the Natural History Museum Zoology. FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS Guraleus costatus (Hedley, 1922) (Fig. 28b) Unfortunately, the specimen was sectioned nearly transversely and an illustration of it comparable with the other species was not possible. Rhynchodeum and proboscis The rhynchodeal sphincter is small and anteriorly located. The epithelium of the anterior part of the rhynchodeal cavity is glandular, whilst that of the posterior rhynchodeum is nonglandular and con- tinuous with that of the proboscis wall. The non-glandular posterior part of the rhynchodeum is
. Bulletin of the Natural History Museum Zoology. FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS Guraleus costatus (Hedley, 1922) (Fig. 28b) Unfortunately, the specimen was sectioned nearly transversely and an illustration of it comparable with the other species was not possible. Rhynchodeum and proboscis The rhynchodeal sphincter is small and anteriorly located. The epithelium of the anterior part of the rhynchodeal cavity is glandular, whilst that of the posterior rhynchodeum is nonglandular and con- tinuous with that of the proboscis wall. The non-glandular posterior part of the rhynchodeum is very thin and attached by numerous muscle fibres to the body wall and probably cannot be everted. The rhynchostome is narrow. The proboscis is very long and coiled, more than twice as long as the rhynchodeal cavity. It is very thick at the base but narrows towards the tip (diameter of mm at the base, but only at the tip). The proboscis walls are thin, comprising less than 17c of the proboscis diameter at its base. The mouth is very narrow. A very small, anterior buccal tube sphincter, lies in front of a small, sac-like enlargement of the buccal tube. The epithelium, lining the enlarge- ment is similar to that of the rest of the buccal tube. A single tooth was seen in the enlargement. There is large intermediate sphincter, situated approximately midway down the proboscis. The buccal tube is very narrow anteriorly, but broad in the posterior part of the proboscis. Its walls are very thin and highly folded. Buccal mass and oesophagus The buccal mass lies within the base of the proboscis, with thick walls and rather broad inner cavity, and showing no curvature. There are large, extensible, buccal lips, which can be inverted inside the cavity. The oesophagus is slightly elongated between buccal mass and nerve ring and forms a short loop. There is no buccal sac. The 81 salivary ducts open into the buccal cavity on both sides of the opening of the radular diverticulum. Glan
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