These diverticula extend usually one into each of the dorsal papillae or " cerata " when these are present.
The Eolid-like Nudibranchs, amongst other specialities of structure, possess (in some cases at any rate) apertures at the apices of the " cerata " or dorsal papillae, which lead from the exterior into the hepatic caeca.
External to the branchia are seen ten club-like processes of the dorsal wall, these are the " cerata " which are characteristically developed in another sub-order of Opisthobranchs.
Herdman, " On the Structure and Functions of the Cerata or Dorsal Papillae in some Nudibranchiate Mollusca," Quart.
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