Note 3 — INTRODUCTION.

The radii have been called by Ranzani and De Blainville “areæ depressæ” (the parietal portions of the compartments being the “areæ prominentes”); by Poli, “areæ interjectæ;” by Gray, “sutures;” by Coldstream, “compartments of the second order,” (the parietal portions being those of the first order); by some authors as “intersticia.” I may here add that the scuta are the “ventral valves” of Gray, the “anterior” of Ranzani, and the “inferior opercular” of De Blainville: the terga are the “posterior valves” of Gray and Ranzani, but the “superior opercular” of De Blainville: the rostrum, on the other hand, is the “anterior valve” of Ferussac and the “ventral” of De Blainville; the carina being the “dorsal valve” of the latter author.