EXPLANATION OF PLATE 31. 53 



the siphuncle is laid bare at a. b. c. d. At e, e, and 

 from thence inwards, it is covered by a soft calcare- 

 ous coating or sheath. 



y. y. Collar, projecting inwards from the transverse plates, 

 and supporting the Siphuncle. See Note, V. I. p. 

 243. 



Fig. 2. Upper horny mandible of the animal, with a hard 

 calcareous point. (Owen.) 



Fig. 3. Lower horny mandible, armed with a similar cal- 

 careous 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 surfaces. (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 Lune- 

 ville. (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-operat- 

 ing 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 



5* 



