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Transactions of the Royal Society of South Africa. 



to its immaturity, is the great increase in the size of the teeth as they are 

 followed backwards, those in the last rows of the radula being more than 

 twice as large as those at the front end. Thus the length of the fourth 

 tooth from the centre is -125 mm. in the first few rows and -255 mm. in the 

 last. The distance between adjacent rows is proportionately increased 

 towards the hind end, and at the same time the angle in the centre of each 

 row becomes somewhat sharper, decreasing from about 130° in front to 

 about 90° behind. 



The radular formula is (24+0+24) X 86. 



The buccal mass in front of the odontophore is long and rather narrow, 

 and extends backwards nearly 2 mm. behind the opening of the oesophagus. 



24 



B. 



Text-fig. 1. — Gonaxis (Eustreptaxis) elongatus Fulton, Macequece. 



A. Representative teeth from the radula of a young specimen ; X 140. 



B. Diagrammatic transverse section through the odontophore of the same specimen. 



The odontophore is thus situated much further back than usual (PL V, 

 fig. 3). Possibly this elongation of the buccal mass may be in order to 

 enable the odontophore to be thrust out further when the walls of the 

 buccal mass are evaginated. In the specimen examined only the lips and 

 the extreme front end of the buccal mass were protruded (fig. 1). 



The oesophagus is not dilated to form a crop. The intestine is straighter, 

 and, consequently, shorter, than usual, a modification often found in 

 carnivorous animals. 



The muscular system is also somewhat specialised. The columellar 

 muscle consists of two main divisions, a broad and powerful ventral muscle 

 to the foot, the so-called tail retractor, and another muscle, which first 

 gives ofi the short, stout buccal retractor, and much further forward divides 

 into both the right and the left tentacular retractors and the other muscles 

 of the front of the head. 



As the specimen examined was quite a young example, its reproductive 

 organs were not sufficiently developed for description. 



