36 
Ichthyosaurici. 
Wall-case, 
No. 14. 
Table-cases, 
Nos. 13, 14. 
two centralia in the carpus of these higher forms is therefore an 
acquired and not an inherited character. 
The structure of the palate is essentially the same as m 
Sphenodon. There is a remarkable resemblance between the 
Ichthyopterygia and the Rhyncliocephalia in the structure ot 
the pectoral arcb, in the presence in both of abdominal ribs , in 
the similar position of the parietal foramen in the cranium, and 
the relation of the quadratojugal to the surrounding bones. In 
both there is the same absence of a lateral \ acuity m ie 
mandible. 
B 
p IG 45 (a) Ventral aspect of the left pectoral limb of Ichthyosaurus Conybeari, (Lydekker), 
Lower Lias, Lyme Regis (£ nat. size), h, humerus; r, radius ; u, ulna ; r, inter- 
medium. The vertical lines show the relative lengths of the limb and the skull, the 
longer line being that of the skull. The notches m the anterior border of the first 
row of phalangeals are omitted, (b) Dorsal aspect of the leL pectoral nmb ot 
Ichthyosaurus communis , (Conybeare), Lower Lias, Lyme Regis. The letters and lines 
are the same as in Fig. A. 
The teeth are confined to the jaws and are implanted in a 
continuous groove, without anchylosis of the bone. Their crowns 
are sharply pointed, and they are usually cylindrical and deeply 
fluted, more rarely carinated, compressed, or smooth (see big. 
-44 a, b, c) . 
