l. Under jaw of Plesiosaurus dolichodeirus, forming part of the series last mentioned. (Original.)

2. head of the Plesiosaurus, figured in PL. 16. Fig. 2. seen from beneath. (Original.)

3. Ventral portion of the ribs of the Plesiosaurus, figured in PL. 17. See V. I. p. 208. (Original.)

a. c. Central bones forming the crown of the sterno-costal arch.

b. triple series of intermediate bones between the central bones, a. c. and the true ribs, d. d. e. e. lower extremity of coracoid bones.