31. The imperforate shell has a turbinate shape. 32. Wall, calcareous, imperforate , porcelaneous. 33. Beginning in 1919 an imperforate variety ( no perforations between stamps ) was also issued. 34. Fifty imperforate blocks were printed on roughly torn paper which were sold to the public. 35. They were uncoloured designs embossed in plain relief on coloured wove paper and were imperforate . 36. The columella is imperforate at its lower extremity, oblique, bearing three unequal folds. 37. The apertural face and peripheral keel, where the two faces meet, are imperforate . 38. The umbilical side is imperforate and smooth. 39. Booklet panes can be associated with any combination of one, two or three imperforate sides. 40. Harrison Proof Cards exist for both values with an imperforate stamp in full colour on each.
