678 



PKOF. T. H. HUXLEY — OBSEBVATIOXS 



is complete at its extremities. The right rib of the third cervical 

 vertebra is 38 millim. long and 10 millim. wide at its head, but it 

 gradually tapers to a point at its ventral end. The fourth cervical 

 vertebra has a rib of similar dimensions, but curved somewhat in 

 the shape of an italic /. This great development of all the anterior 

 cervical ribs is a point of contrast between Hyperodapedon and Sphe- 

 nodon, in which last only rudiments of such ribs are discoverable. 



The fifth cervical vertebra is almost completely hidden under the 

 shoulder-girdle, behind which a vertebra makes its appearance, 

 which I take to be the 9th, though it may be the 10th. The cen- 

 trum of this vertebra is 20 millim. long, 25 millim. wide between 

 the ends of the transverse processes in front, and 17 millim. wide 

 in the middle of its length ; and the centra of the three vertebrae which 

 follow it have similar dimensions and appear to have concave posterior 

 faces. These vertebras have strong but short transverse processes. 

 That of the 11th vertebra, on the right side, shows a roilnded surface 

 for the articulation of the head of the rib. The vertebral end of this 

 rib is also well displayed ; it is broad, measuring 20 millim. from its 

 dorsal to its ventral margin, which is concave and thick, while the 

 dorsal margin is thinner and convex (Plate XXVI. fig. 9). The 

 vertebral end of a similar rib is visible on the right side, close to the 

 16th vertebra, and there are less well-preserved remains of others. 

 These ribs are very similar to the corresponding ribs of Sphenodon. 



Nearly the whole length of the rib which belongs to the 12th or 

 13th vertebra is shown ; it is about 12 millim. broad, flattened 

 and truncated at the sternal end ; it measures 153 millim. along 

 the chord of the arc of its curvature. The vertebral end is not 

 completely exposed. 



A thin flat plate of bone, 20 millim. long by 14 millim. wide, is 

 seen on the right side, overlying the remains of two vertebral ribs, 

 opposite the 14th vertebra. I suspect that this is a "processus 

 uncinatus " such as those which occur in Sphenodon. The position 

 of the skeleton is unfavourable for showing such bones, if they were 

 preserved, and they would readily become detached. Portions of 

 eight ribs, in undisturbed series, corresponding to the vertebras from 

 the 18th to the 22nd inclusively, are seen on the right side. It is 

 possible that these may be the ends of vertebral ribs ; but I incline to 

 the supposition that they are sternal ribs, because the inner trun- 

 cated end of each is in close relation with a bundle of five or six lateral 

 abdominal ossicles, of which the central ossicles in each bundle are 

 nearly straight, while the anterior and posterior describe elliptical 

 curves. If these are really sternal ribs, they are very different, in 

 form, from those of Sphenodon* . It is by no means easy to 

 arrive at a clear notion of the nature and arrangement of the abdo- 

 minal ossicles, which extend over the ventral surface between the 

 sternum and shoulder-girdle in front, and the pelvis behind. In 

 front there is an area covered by ossicles of a V shape, the point 



* Dr. Baur has stated that the abdominal ossicles of Sphenodon are con- 

 nected by ligament in pairs with the sternal ribs, but I have not yet been able 

 to satisfy myself of the fact. 



