 The spermatophores of males are about 4 @.@ 5 mm ( 0 @.@ 18 in ) long and 0 @.@ 15 mm wide . The ink sac is pear @-@ shaped , with a silvery blue @-@ green outer layer . The vane of the gladius ( the rigid internal remnants of the mollusc shell ) is oval @-@ shaped and pointed at both ends ( lanceolate ) . It has a broad midrib ( rachis ) . 
