Editing Tusk shell (section)

==Orientation==
The morphological shape of the scaphopod body makes it difficult to orient it satisfactorily.  As a result, researchers have often disagreed as to which direction is anterior/ posterior and which is ventral/ dorsal.  According to [[Ronald Shimek|Shimek]] and Steiner, "[t]he apex of the shell and mantle are anatomically dorsal, and the large aperture is ventral and anterior.  Consequently, the concave side of the shell and viscera are anatomically dorsal.  The convex side has to be divided into anteriorly ventral and dorsally posterior portions, with the anus as the demarcation.  Functionally, as in [[cephalopod]]s, the large aperture with the foot is anterior, the apical area posterior, the concave side dorsal and the convex side ventral."<ref>{{cite book|title=Microscopic anatomy of invertebrates|volume=6B: Mollusca II|last1=Shimek|first1=Ronald|last2=Steiner|first2=Gerhard|chapter=Chapter 6|publisher=Wiley-Liss, Inc.|date=1997|page=719}}</ref>