has part homologous_to chitin gladius The chitinous remnant of the shell in many decapodiforms and <strong>Vampyroteuthis</strong>. It is generally feather-shaped and lies in the dorsal mid-line of the body along the full length of the mantle. The gladius lies within the shell sac which secretes it. The gladius, found in many decapodiforms and Vampyroteuthis, is an internal remnant of the originally external shell of cephalopods. Other cephalopods have other types of shell remnants. The gladius lies within a sac, the shell sac, which secretes it and to which various muscles attach. The gladius has a variety of shapes and thicknesses, is composed mostly of chitin and is located in the dorsal midline and generally extends the full length of the mantle. Conus field - The lateral portion of the gladius that is continuous posteriorly with the primary conus or its remnant and laterally with the edges of the vanes. The conus field is differentiated from the vanes by longitudinal lines and marked changes in the orientation of the growth lines. A conus field is generally lacking if the gladius lacks a primary conus. http://tolweb.org/tree/ToLimages/Gladius.jpg pen internal gladius gladii organism subdivision shell