. Bulletin of the British Museum (Natural History) Zoology. MORDAN 11. Fig. 16 A. Epiphallus; B. Penial appendix; C. Penis. Edouardianatalensis, Pietermaritsberg, South Africa. Scale line 1 mm. genera were readily classified as lip present or absent. In most genera the umbilicus (Character 19) remains open, although it can vary from widely gaping (eg. Conulinus) to minute (), but in Euryptyxis and it becomes closed off. These last two genera additionally develop a columellar fold or ridge (Character 18) which is clearly visible in the aperture, and which may
. Bulletin of the British Museum (Natural History) Zoology. MORDAN 11. Fig. 16 A. Epiphallus; B. Penial appendix; C. Penis. Edouardianatalensis, Pietermaritsberg, South Africa. Scale line 1 mm. genera were readily classified as lip present or absent. In most genera the umbilicus (Character 19) remains open, although it can vary from widely gaping (eg. Conulinus) to minute (), but in Euryptyxis and it becomes closed off. These last two genera additionally develop a columellar fold or ridge (Character 18) which is clearly visible in the aperture, and which may become consid- erably enlarged further back within the body whorl (Mordan, 1986). Radula (Characters 20-22) In separating the Cerastinae (or Pachnodinae) from the northern Enidae, Watson (1920: 23) noted that in many cerastine species 'most of the teeth of the radula, instead of having their major axes practically in a line with one another, are placed more or less obliquely, so that the outer side of one tooth is in front of the inner tooth next beyond'. In Pachnodus (van Mol & Coppois, 1980) there is a clear backward angulation of the marginal teeth relative to the laterals, which lie in a relatively straight row. By way of contrast, in all eleven species of Rhachistia and one of Amimopina whose radulae were examined in the present study, the entire row is angled forward in a V shape from the central tooth at a fairly constant angle of about 110°. Both these patterns are distinct from the weakly arcuate row form characteristic of the remaining cerastine genera and the Eninae (Mordan, 1986: Fig. 19e). Thus three states of radu- lar row pattern are recognised in the analysis (Character 20). In most of the cerastines examined, tooth form is fairly uniform: the central mesocone is pointed and bears a pair of smaller ectocones; laterals have a similarly pointed mesocone with well-developed ectocone but no endocone; and the marginals carry blunt, rounded mesocones and ectocone
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