62 



Y.I. KANTOR, A. MEDINSKAYA AND J.D. TAYLOR 



Fig. 7 Crassispira (Crassispirella) latizonata (Smith, 1882). Longitudinal section of the posterior part of the proboscis and buccal mass (only one salivary 

 duct is shown). 



Rhynchodeum and proboscis 



The rhynchostomal sphincter is small and anteriorly located. The 

 epithelium of the anterior half of the rhynchodeal wall is glandular, 

 arranged into high folds, but to the posterior it is continuous with that 

 of the proboscis wall. The dorsal wall of the proboscis tip is inverted 

 inside. The proboscis is medium long (about half of the rhynchocoel) 

 and not coiled. The muscles of the proboscis wall are equally 

 developed along its length. 



There is a small, anterior buccal tube sphincter, which lies in front 

 of the well developed, sac-like enlargement of the buccal tube, lined 

 with tall epithelium. There is no epithelial pad. A large, intermediate 

 sphincter of the buccal tube is present, which lies at the base of the 

 distal enlargement at a distance of about 2.5 radular tooth lengths 

 from the mouth opening. The proboscis walls are not thick, compos- 

 ing about 15% of proboscis diameter. The wall of the buccal tube 

 wall is also not thick, forming about 8% of proboscis diameter. 

 Small buccal lips are present. 



Buccal cavity and oesophagus 



The buccal mass lies posterior to the proboscis base and is large, 

 equivalent to about one quarter of proboscis length. Anterior to the 

 opening of the radular sac, the walls of the buccal cavity are thin, 

 similar to those of the buccal tube, but become thicker to the 

 posterior. 



The oesophagus is greatly elongated between the buccal mass and 

 nerve ring and forms a very long loop. A remarkable feature of the 

 oesophagus is that its epithelium bears very long cilia which occupy 

 the whole lumen.The duct of the radular sac is broad and rather long. 

 The buccal sac very short. 



Glands 



The salivary glands are tubular in histology, coiled and situated near 

 the nerve ring. The salivary ducts are very long, coiled and thick. The 

 histology of the venom gland changes abruptly after passing through 

 the nerve ring. The duct of the venom gland is ciliated, coiled and 

 narrow, with the same diameter as the salivary ducts, and opens into 

 the buccal cavity at the border with the oesophagus. The muscular 

 bulb is large, with thick walls formed of two layers of longitudinal 

 muscle fibres, divided by a connective tissue layer, with a much 

 thinner, innermost layer of circular fibres. 



Odontophore and radula 



The odontophore is rather large and consists of paired subradular 

 cartilages, formed by single layer of cells. The radula was not 

 examined and there are, unfortunately, no published illustrations. 



Crassispira (Monilispira) pluto Pilsbry and Lowe, 1932 



(Fig. 11a) 



Rhynchodeum and proboscis 



The rhynchostomal sphincter is large and anteriorly situated. The 

 epithelium of the anterior seven eighths of the rhynchodeal wall is 

 tall, glandular and arranged into high folds, while that of the 

 posterior one eighth is continuous with the proboscis wall. The 

 proboscis tip is not infolded. The proboscis is very long (ca 1 .5 times 

 longer than rhynchocoel), coiled in the anterior part and thick. The 

 muscles of the proboscis wall are more developed at the base. 



An anterior buccal tube sphincter is present. The sac-like enlarge- 

 ment of the buccal tube is present, but not well differentiated. Also, 

 there is an epithelial pad with a marginal tooth attached to it. An 

 intermediate sphincter is absent. The proboscis walls are thick, 

 comprising about 20% of proboscis diameter, whilst the buccal tube 

 wall is medium-thick, forming about 15% of the total diameter. The 

 buccal lips are large and muscular. 



Buccal mass and oesophagus 



The buccal mass lies posterior to the proboscis, is rather long, with 

 thick walls, uncurved and equivalent to about half the proboscis 

 length. The oesophagus is elongated between the buccal mass and 

 nerve ring and forms a long loop. The buccal sac is very short. 



Glands 



The salivary glands are large and acinous. The histology of the 

 venom gland changes after passing the nerve ring. The duct of the 

 venom gland is narrow and unciliated. The gland itself is long. The 

 muscular bulb was unfortunately missing from the sections. 



Odontophore and radula 



The odontophore is large, consisting of paired, unfused, subradular 

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



