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 length. There 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 

 mass. The 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. 



Odontophore and radula 



The odontophore is medium-sized with paired, unfused cartilages. 

 The radula consists of only marginal teeth of the wishbone type, with 

 the major limb robust, solid and pointed with a long straight leading 

 edge. The minor limb is smaller and thinner, but tapers towards the 

 base (Fig. 4b). The marginal tooth is short, ca. 130um (0.3% of SL, 

 1.0% AL). 



