determined the apical angle ö¡ and measured the ratio R; as follows:
| R | ö¡ | öÝ | |
|---|---|---|---|
| Turritella sp. | 1ôñ12 | 7ô¯ | 81ô¯ |
| Cerithium nodulosum | 1ôñ24 | 15ã | 82ã |
| Conus virgo | 1ôñ25 | 70ã | 88ã |
| Mitra episcopalis | 1ôñ43 | 16ã | 78ã |
| Scalaria pretiosa | 1ôñ56 | 26ã | 81ã |
| Phasianella bulloides | 1ôñ80 | 26ã | 80ã |
| Solarium perspectivum | 1ôñ50 | 53ã | 85ã |
| Natica aperta | 2ôñ00 | 70ã | 83ã |
| Planorbis corneus | 2ôñ00 | 90ã | 84ã |
| Euomphalus pentangulatus | 2ôñ00 | 90ã | 84ã |
We see from this that shells so different in appearance as Cerithium, Solarium, Natica and Planorbis differ