THE CARNIVOROUS SJ.UGS OF SOUTH AFRICA. 165 



handbill A. burnupi and A. sexangula the aperture is 

 very small, and the front end of the support is pointed 

 (see fig. 112). The hind end of the odontophoral support is 

 rather abruptly truncated. Along the inner surface of the 

 support there runs a median longitudinal furrow, which can 

 be best seen in transverse sections of the odontophore of 

 A. dimidia (PI. XVIII, figs. 116-121). In the other species 

 it is not usually so well marked. 



The odontophoral support is flexible, but much firmer than 

 ordinary muscular tissue, and it is usually semi-translucent ; 

 yet it does not contain any cartilage, but is entirely com- 

 posed of long narrow cells stretching radially from the inner 

 to the outer surface (PI. XVI, fig. 90). The nuclei of these 

 cells are also lengthened, and are rather more numerous 

 towards the outer than the inner surface of the support, 

 doubtless because the cells are on an avei'age slightly broader 

 towards the outside. Most authors have regarded these long 

 cells which occur in the odontophoral support of carnivorous 

 snails and slugs as being muscle-fibres; but Beutler^ has 

 disputed this view, and has maintained that in Paryphanta 

 hochstetteri {Pfr.) this tissue is not muscular. Now, I 

 should certainly not be inclined to consider these cells as 

 being of the nature of ordinary muscu.lar fibres in Apera, 

 but they might perhaps be regarded as muscle-fibres which 

 have become modified for a supporting or skeletal purpose, 

 and, if this is so, it is possible that they have become more 

 modified in genera such as Paryphanta and Apera than 

 in the types studied by Plate. In Testacella and Daude- 

 bardia there are longitudinal muscle-fibres and other cells 

 intercalated among the radial elements of the support,'^ and I 

 have found that this is also the case in Euglandina 

 venezuelensis [Preston); but these are entii'ely absent in 

 Apera, as in Paryphanta'' and Natalina.^ 



' Op. cit., pp. 380, 381. 

 Plate, L. H., ' Zool. Jalirb.,' 1891, vol. iv, pi. xxxiii, figs. 30, 31, 39, 

 41, pi. xxxiv, fig. 51. 



^ Bentler, op. cit., p. 380. 



* Woodward. M. F.. ' Proc. Mai. Soc," 1895, vol. i, p. 273. 



