whorls. The following table gives a few illustrations of this ratio in particular cases, in addition to those which we have already studied. {557}
| Pointed Turbinates | Obtuse Turbinates and Discoids | |||
|---|---|---|---|---|
| ã Telescopium fuscum | 1ôñ14 | ô | ã Conus virgo | 1ôñ25 |
| ã Acus subulatus | 1ôñ16 | ô | ã Conus litteratus | 1ôñ40 |
| * Turritella terebellata | 1ôñ18 | ô | ã Conus betulina | 1ôñ43 |
| * Turritella imbricata | 1ôñ20 | ô | * Helix nemoralis | 1ôñ50 |
| ã Cerithium palustre | 1ôñ22 | ô | * Solarium perspectivum | 1ôñ50 |
| ã Turritella duplicata | 1ôñ23 | ô | ã Solarium trochleare | 1ôñ62 |
| ã Melanopsis terebralis | 1ôñ23 | ô | ã Solarium magnificum | 1ôñ75 |
| ã Cerithium nodulosum | 1ôñ24 | ô | * Natica aperta | 2ôñ00 |
| * Turritella carinata | 1ôñ25 | ô | ã Euomphalus pentangulatus | 2ôñ00 |
| ã Acus crenulatus | 1ôñ25 | ô | ã Planorbis corneas | 2ôñ00 |
| ã Terebra maculata (Fig. 285 ) | 1ôñ25 | ô | ã Solaropsis pellis-serpentis | 2ôñ00 |
| * Cerithium lignitarum | 1ôñ26 | ô | ã Dolium zonatum | 2ôñ10 |
| ã Acus dimidiatus | 1ôñ28 | ô | * Natica glaucina | 3ôñ00 |
| ã Cerithium sulcatum | 1ôñ32 | ô | ã Nautilus pompilius | 3ôñ00 |
| ã Fusus longissimus | 1ôñ34 | ô | ã Haliotis excavatus | 4ôñ20 |
| * Pleurotomaria conoidea | 1ôñ34 | ô | ã Haliotis parvus | 6ôñ00 |
| ã Trochus niloticus (Fig. 286 ) | 1ôñ41 | ô | ã Delphinula atrata | 6ôñ00 |
| ã Mitra episcopalis | 1ôñ43 | ô | ã Haliotis rugoso-plicata | 9ôñ30 |
| ã Fusus antiquus | 1ôñ50 | ô | ã Haliotis viridis | 10ôñ00 |
| ã Scalaria pretiosa | 1ôñ56 | ô | ô | ô |
| ã Fusus colosseus | 1ôñ71 | ô | ô | ô |
| ã Phasianella bulloides | 1ôñ80 | ô | ô | ô |
| ã Helicostyla polychroa | 2ôñ00 | ô | ô | ô |
| Those marked * from Naumann; the rest from Macalisterÿ£¢ 526 . |
In the case of turbinate shells, we require to take into account the angle ö¡, in order to determine the spiral angle öÝ from the ratio of the breadths of consecutive