explanation of plates 12. 13. 
25 
A. 
B. 
D. 
Hollow conical Vertebra of a fish. (Original.) 
C. E. Vertebrae of Ichthyosaurus. See Note, V. I. 
p. 1/8. (Home and Conybeare.) 
a. g. E. a. g. Spinous processes, shewing the peculiar 
articulation of their annular portions, with the Ver- 
tebra, to be adapted to increase the flexibility of the 
spine. See Note, V. I. p. 179. (Home.) 
Plate 13. V. I. p. 190. 
Skeleton of a small Ichthyosaurus, from the Lias at 
Fig- 4, 1). Oblique triangular facet on the lower margin of the 
rontof the Atlas; this facet articulated witli the first sub-vertebral 
"edge, placed between the Atlas and Occiput. 
Between the Atlas and Axis, the two sub-vertebral facets formed a 
riangular cavitj. for the reception of a second wedge (Fig. 4. c.) 
and a similar, but smaller cavity received another wedge of the 
same kind, between the Axis and third Vertebra. This third wedge 
gave less support to the head, and admitUul of more extensive mofiou 
than the second. All these three wedge-shaped bones are seen 
neatly in their natural position in a specimen from Lyme Regis, in 
le Collection of Sir P. G, Fgerton, 
of t 1 ^ sub-vertebral wedge, auxiliary to the anterior cavity 
nr., completing the articulating socket for the basilar 
process of the Occiput (3. a). 
a. Crescent shaped front of the first sub-vertebral wmdge. 
^ • • Head ol the same Wedge. 
frontal ftm*!*"** artictilaliug with the triangular 
is nearl -A-tlas (4. b.). In young animals this frontal facet 
furrowed c^ler animals (3. b'.) it is rugged and 
wedge great *o must have given to the firstsub-vertebral 
sure of the head'^'^^^'* downward pre.s- 
wents of the OccipUal bone"’*' 
gulai^ cayT ®ob-vertebral wedge articulating with the triaii- 
Lhis Second niarginal facets of the Atlas and Axis, 
lower no c' acted as a strong prop supporting firmly the 
oVrol?h;re 
i®c'mglot;Vs'riKl ® 
