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J.D. TAYLOR, Y.I. KANTOR AND A.V. SYSOEV 



tip (Fig. 12). This sac is covered in granule-like structures 

 which are formed from single cells with large rounded nuclei. 

 The distinctive epithelial cells seen at the proboscis tip of 

 Mangelia nebula by Sheridan et al. (1973) may be the same 

 structure but in a more contracted position. The function of 

 this sac structure is not known. 



Position of the buccal mass 



Three conditions are known in the Conoidea; 



a) Buccal mass situated at the base of the proboscis (Fig. 1 ) 

 For three reasons we consider this condition to be the 

 primitive state within the Conoidea. Firstly, a basal buccal 

 mass is found in species of the subfamily Drilliinae, which 

 with five teeth in each radula row, are considered to possess 

 the least-derived type of radula. Secondly, and also in the 

 Drilliinae, there is a muscular connection between the retrac- 

 tor muscle of the radular sac and the columellar muscle 

 (Kantor, 1990). This is a condition found in some meso- and 

 archaeogastropods, as for example in Littorina, Cryptonatica 

 and Tegula (Fretter & Graham, 1963; Kantor, unpublished 

 observations). In most other probosciform gastropods, 

 including those turrids where the buccal mass lies within the 

 proboscis, this connection is broken and the radula is con- 

 nected by muscles to the walls of the proboscis. Finally, the 

 basal buccal mass is a character-state shared amongst most of 

 the subfamilies of Turridae, along with the Terebridae, 

 Pervicaciidae and Conidae. 



b) Buccal mass located within the proboscis 



In Clavatula diadema (Clavatulinae), the buccal mass lies 

 within the proboscis, but in a proximal position (Kantor, 

 1990, fig. 8). In Clionella sinuata (Clavatulinae), Pilsbryspira 

 nympha (Zonulispirinae) and Funa latisinuata (Crassispiri- 

 nae), it lies more anteriorly, about half way along the 

 proboscis (Figs 6 & 14). In Strictispira paxillus (Strictispiri- 



nae) (Fig. 13), Toxiclionella tumida (Clavatulinae) (Kantor, 

 1990 fig. 4), and Turricula nelliae spurius (Cochlespirinae) 

 (Taylor, 1985; Miller, 1990), the buccal mass lies in a distal 

 position near the tip of the proboscis. 



The distally shifted position of the buccal mass in these few 

 turrids is a derived condition, being found only in some 

 species of the subfamilies Clavatulinae, Cochlespirinae 

 Zonulispirinae and Strictispirinae. 



c) Buccal mass situated a long way to the posterior of the 

 proboscis base (Kantor, 1990, fig. 1). 



This condition is found only in Hormospira (Pseudome- 

 latominae) and described by Kantor (1988). 



Elongation of the oesophagus to the anterior of the 

 circum-oral nerve ring 



In some turrids the oesophagus is elongated into a curved 

 loop between the base of the proboscis and the circum-oral 

 nerve ring (Fig. 14). This elongation is found in those turrids 

 with a buccal mass situated within the proboscis, and allows 

 forward movement of the buccal mass on protraction of the 

 proboscis. This condition is found in Clavatulinae. Stric- 

 tispirinae, Turricula nelliae spurius (Cochlespirinae), Cras- 

 sispirinae such as Funa latisinuata, and Pilsbryspira 

 (Zonulispirinae). 



Buccal lips (inner buccal tube) 



These consist of muscular extensions of the anterior walls of 

 the buccal mass, which protrude as a tube into the lumen of 

 the buccal tube (Figs 1 & 9). In Oenopota levidensis where 

 the buccal lips are long (Shimek, 1975), they form a second 

 'proboscis' within the true proboscis. At full contraction of 

 the true proboscis, the tube formed by the buccal lips 

 protrudes through the mouth. Shimek (1975) called this 

 secondary 'proboscis' the buccal tube. Various developments 



0-5mm 



Fig. 9 Mangelia nebula; longitudinal section through the proboscis. A, with buccal lips protracted; B, radular tooth in proboscis and buccal 

 lips withdrawn into the buccal cavity. After Sheridan et al. (1973, fig. 7) & Delaunois & Sheridan (1989, plate II). Abbreviations: be, buccal 

 cavity; bl, buccal lips; ds, distal sphincter of buccal tube; i, buccal tube introvert; m, mouth; ps, posterior sphincter of buccal tube; t, 

 radular tooth. 



