Fig. I . Animal of Nautilus Pompilius, fixed in its shell. The shell is copied from one in the collection of Mr. W. I. Broderip. (Animal from Owen. Shell original.)

n. The Hood, or ligamento-muscular disk that surrounds the head.

p. The digital tentacles protruded from their sheaths.

k. Funnel.

a. b. c. d. e. Siphuncle. The desiccated membrane of [053] the siphuncle is laid bare at a. b. c. d. At e, e, and from thence inwards, it is covered by a soft calcareous coating or sheath.

y. y. Collar, projecting inwards from the transverse plates, and supporting the Siphuncle. See Note, V. I. p. 322.

Fig.2. Upper horny mandible of the animal, with a hard calcareous point. (Owen.)

Fig. 3. Lower horny mandible, armed with a similar calcareous point. (Owen.)

Fig. 4. Calcareous point, and palate of upper mandible separated from the horny portion. (Owen.)

Fig. 5. Under surface, or palate of a Rhyncholite, or fossil beak, from the Lias at Lyme Regis, analogous to the recent specimen, fig. 4. (Original.)

Fig. 6. Upper view of another Rhyncholite from the same stratum and place. Black portions of the horny substance, in a state resembling charcoal, remain attached to its posterior stirfaces. (Original.)

Fig. 7. Side view of the calcareous portion of an upper mandible, from the Muschel kalk of Luneville. (Original.)

Fig. 8. Upper view of another Rhyncholite from Luneville. (Original.)

Fig. 9. Palatal view of fig. 8. (Original.)

Fig. 10. Calcareous point of an under mandible from Luneville. The dentations on its margin resemble those on the recent mandible, fig. 3, and co-operating with the dentations on the Margin of the upper mandible, fig. 9, must have formed an Instrument (like the recent beak, figs. 2 and 3,) well fitted for the rapid demolition of Crustacea and small Shells. (Original.)

Fig. 11. Under surface of fig. 10.; it is strengthened by [054] a double keel-shaped indented process, enlarging from its apex backwards.* (Original.)

Although the resemblances between these fossil beaks, and that of the animal inhabiting the N. Pompilius, are such as to leave no doubt that Rhyncholites are derived from some kind or other of Cephalopod, yet, as they are found insulated in strata of Muschel kalk and Lias, wherein there occur also the remains of Sepiæ that had no external shells, we have not yet sufficient evidence to enable us to distinguish between the Rhyncholites derived from naked Sepiæ, and those from Cephalopods that were connected with chambered shells. I possess a specimen of a fossil Nautilus from the Lias at Lyrne Regis, in which the external open chamber contains a Rhyncholite.