FOREGUT ANATOMY AND CLASSIFICATION OF CONOIDEA 



od rs 



131 



bts 



Fig. 6 Clionella sinuata;A, longitudinal section through the 

 foregut; B, section of tip of proboscis showing sphincters; C, 

 section of portion of the inner wall of the rhynchodeum. showing 

 the differentiation in epithelium from that similar to the proboscis 

 wall, to that typical of the lining of the rhynchocoel. 

 Abbreviations: bm, buccal mass; bts, buccal tube sphincters; con, 

 circum-oral nerve ring; mb, muscular bulb; od, odontophore; oe, 

 oesophagus; p, proboscis; rhs, rhynchostomal sphincter; rs. 

 radular sac; sg, salivary gland; tec, tall epithelial cells; vg, venom 

 gland. 



Sac-like enlargement of buccal tube 



One other character associated with the gripping of marginal 

 teeth at the proboscis tip, is the presence of a sac-like 

 en-largement of the anterior or middle parts of the buccal 

 tube. It is found in different 'lower' turrids (Kantor & Taylor, 

 1991) as well as Mangelia nebula (Sheridan et ai, 1973) and 

 Conidae (Conns catus (Greene & Kohn, 1989) and C. ventri- 

 cosus). Usually, the epithelium lining the enlargement is 

 formed of much taller cells than in the rest of the buccal tube. 

 These cells tightly surround the single radular teeth whilst 

 they are being held at the proboscis tip and may afford a 

 better grip. In Splendrillia chathamensis , Sysoev & Kantor 

 (1989) found the base of tooth adhering to a pad of epithelial 

 cells. 



Protrusive lips of proboscis! buccal tube 



In a few species, the inner lining of the outer lips of the 

 proboscis can be protruded. For example, in Turricula nelliae 

 spurius, the lips (Fig. 11) are densely covered by paddle or 

 discocilia, which according to Haszprunar (1985) may indi- 

 cate the presence of chemosensory cells. Similar protrusible 

 lips are also found in Lophiotoma leucotropis and probably in 

 Aforia aulaca alaskana (Sysoev & Kantor, 1987). 



In relaxed specimens of Mangelia powisiana, a sac consist- 

 ing of a single layer of cells is protruded from the proboscis 



ovg 



rhs 



sng 



Fig. 7 Conus ventricosus; longitudinal section of the foregut 

 showing the proboscis retracted into the rhynchodeum. 

 Abbreviations; bm, buccal mass; bts, buccal tube sphincter; dasg, 

 duct of accessory salivary gland; fpw, fold of proboscis wall; ors, 

 opening of radular sac; ovg, opening of venom gland; p, 

 proboscis; rhs, rhynchostomal sphincter; sng, snout gland. 



5mm 



Fig. 8 Gymnobela emertoni: longitudinal section of the foregut 

 showing, the remnants of the proboscis, buccal lips and vestigial 

 radular sac. Abbreviations: bl, buccal lips; con, circum-oral nerve 

 ring; m, mouth; pr, reduced proboscis; rhs, rhynchostomal 

 sphincter; rm, radial muscles in rhynchodeal wall; rs, radular sac; 

 sg, salivary gland. 



