ds ▁split ▁or ▁are ▁inter cal ated . ▁Sp ire ▁is ▁con ic . ▁The ▁shell ▁has ▁ 3 ½ - 4 ▁moder ately ▁convex ▁wh or ls . ▁The ▁last ▁wh or l ▁is ▁glo bose . ▁The ▁s uture ▁is ▁slowly ▁desc ending ▁in ▁front . ▁A pert ure ▁is ▁rounded - ov ate , ▁very ▁ob lique , ▁the ▁outer ▁lip ▁thin , ▁its ▁upper ▁end ▁inserted ▁at ▁or ▁near ▁the ▁peri ph ery ▁of ▁the ▁pen ult imate ▁wh or l . ▁The ▁col um ell ar ▁lip ▁is ▁very ▁thin ▁and ▁regularly ▁ar cu ate . ▁ ▁The ▁width ▁of ▁the ▁shell ▁is ▁ 1 0 . 7 - 1 4   mm ; ▁the ▁height ▁of ▁the ▁shell ▁is ▁ 1 1 . 7 - 1 4   mm . ▁The ▁width ▁of ▁the ▁a pert ure ▁is ▁ 9 . 5   mm ; ▁the ▁longest ▁axis ▁of ▁the ▁a pert ure ▁is ▁ 1 2 . 4   mm . ▁ ▁References ▁This ▁article ▁incorpor ates ▁public ▁domain ▁text ▁from ▁the ▁reference ▁ ▁External ▁links ▁▁▁▁ ▁Category : S imp ul ops idae ▁Category : G ast rop ods ▁described ▁in ▁ 1 8 4 6 ▁Category : Art icles ▁containing ▁video ▁cli ps <0x0A> </s> ▁" Le is ure " ▁is ▁a ▁poem ▁by ▁Wel sh ▁poet ▁W . ▁H . ▁Dav ies , ▁appearing ▁originally ▁in ▁his ▁Songs ▁Of ▁Joy ▁and ▁O thers , ▁published ▁in ▁ 1 9 1 1 ▁by ▁A