complicated form of the suture-line, and studying the form of the liquid film which constitutes the corôÙreôÙsponôÙding surface minimae areae.
In certain Ammonites the septal outline is further complicated in another way. Superposed upon the usual sinuous outline, with its ãlobesã and ãsaddles,ã we have here a minutely ramified, or arborescent outline,
in which all the branches terminate in wavy, more or less circular arcs,ãlooking just like the ãlandscape marbleã from the Bristol Rhaetic. We have