FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS 



61 



Fig. 6 Crassispira (Glossispira) harfordiana flucki (Brown & Pilsbry, 1913). A, semidiagrammatic longitudinal section of the foregut (salivary glands not 

 shown); B, longitudinal section of the proboscis tip; C, section of the buccal mass, showing the opening of the radular sac. 



Crassispira (Glossispira) harfordiana flucki (Brown & 

 Pilsbry, 1913) 



(Figs 4d, 6, 30e) 



Rhynchodeum and proboscis 



The rhynchostomal sphincter is small and slightly posteriorly situ- 

 ated. The epithelium of the rhynchodeum wall is glandular and that 

 of the posterior rhynchodeal wall is not continuous with that of the 

 proboscis wall. The proboscis tip is not inverted. The proboscis is 

 very long and highly coiled (longer than the rhynchocoel and shown 

 uncoiled in Fig. 6). The muscles of the proboscis wall are equally 

 developed along its length, except at the very anterior. 



The anterior part of the proboscis from the mouth opening to the 

 buccal mass is very thin (about 0. 1 mm compared to the proboscis 

 length of about 5-6 mm) and highly folded. The proboscis tip is 

 highly expanded to form a wineglass-shaped structure (Fig. 6, 30e). 

 Closer to the tip, there is a septum with a small, circular sphincter 

 surrounding the narrow opening. The septum delimits the sac-like 

 enlargement of the buccal tube. The epithelium lining this is signifi- 

 cantly taller than that of the rest of the tube, forming a low epithelial 

 pad. At the base of the enlargement, there is a second small sphincter. 

 Pieces of one, or possibly more, marginal teeth (fragmented during 

 sectioning) were seen attached to the epithelium. The distance 

 between the two sphincters corresponds to about one tooth length. It 

 is possible, that the enlargement serves as a storage area for detached 

 marginal teeth. There is no intermediate sphincter in the buccal tube. 



Buccal cavity and oesophagus 



The buccal mass is long (equivalent to about one quarter of probos- 

 cis length), with moderately thick walls and no curvature. It is 



contained entirely within the proboscis and starts within the distal 

 third of the proboscis length. The walls of the buccal cavity form 

 several annular folds. The buccal lips are small. 



The oesophagus is highly elongated between the buccal mass and 

 nerve ring, but because the buccal mass is located anteriorly within 

 the proboscis, there is virtually no loop. A buccal sac is absent. The 

 opening of the radular diverticulum into the buccal cavity is narrow 

 and bordered by a rather tall circular muscular fold. The salivary 

 ducts open into the cavity at the base of this fold (Fig. 6). 



Glands 



The salivary glands are small, paired and acinous and lie at the 

 proboscis base. The ducts are highly coiled. The histology of the 

 venom gland changes abruptly after passing through the nerve ring. 

 The duct of the venom gland is unciliated, narrow, and highly coiled 

 before opening into the buccal cavity at the border with the oesopha- 

 gus. The muscular bulb is large, with thick walls formed of two 

 layers of longitudinal muscle fibres, separated by a connective tissue 

 layer, with a much thinner innermost layer of larger circular fibres 



Odontophore and radula 



The odontophore is small and composed of a pair of unfused 

 cartilages formed by a single layer of cells. The radula consists of 

 marginal teeth of the wishbone type (Fig. 4d), with a solid, pointed, 

 curved major element and a shorter and narrower secondary ele- 

 ment. The marginal tooth is medium long, ca. 195pm (0.7% of SL, 

 2.7% AL). 



Crassispira (Crassispirella) latizonata (E. A. Smith, 1 882) 

 (Fig. 7) 



