206 Dr. T. F. Jamieson — Changes of Level 



A fragment of the upper end of the right humerus fits on the 

 impression of its anterior face, which is correctly identified by Owen. 

 (loc. cit., pi. xiii, fig. 2, H). 



Impressions of the right ulna and radius are preserved on the slab 

 of Greensand described by Owen as exhibiting the shaft of a tibia and 

 the lower end of a fibula (loc. cit., p. 49, pi. xiii, fig. 1). The ulna, 

 which seems to lack only a short piece at its upper end, is a relatively 

 stout bone about 60 cm. in length. Its upper portion is trihedral, 

 with each of the three faces a little indented in the middle and 

 measuring respectively 13, 15, and 17 cm. across. One view of it is 

 drawn, upside down, in Owen's pi. xii, fig. 2, as a "lower end of 

 shaft of humerus." A fragment of this region, showing the posterior 

 indented face and two angles, is also represented in cross-section by 

 Owen in his text-fig. 2, p. 50, as if it were complete, while the extent 

 of the central loose tissue is hypothetieally and erroneously shaded. 

 Further down the ci'oss-section is nearlj' as shown in Owen's text- 

 fig. 1, p. 50. The distal end, which, is complete and exhibits the 

 usual pitted surface for a cap of cartilage, is represented by Owen in 

 his text-fig. 6, p. 51, while the cross-section 15 cm. higher up is given 

 in text-fig. 7, p. 51. The bone is less expanded at the upper end than 

 in Cetiosaurus and Morosaurus. The radius itself is not preserved, and 

 only the upper half of it is seen in impression. It evideiitly conforms 

 to the Cetiosaurian pattern. 



Of the other fragments of Dinodocus, it suffices to remark that none 

 of them are metatarsals or other foot-bones. The specimen shown in 

 Owen's text-figs. 10 and 11, p. 52 (also in pi. xiii, fig. 5), suggests the 

 distal end of a fibula. 



It is thus evident that Dinodocus is a large Sauropodous Dinosaur, 

 with a remarkably slender fore-limb. In its slenderness the humerus 

 differs from that of Cetiosatirus and Morosaurus, while agreeing exactly 

 with the Wealden humerus named Pelorosaurus by Mantell.^ There 

 is, in fact, no justification at present for regarding Pelorosaurus and 

 DiHodocus as distinct genera. As already remarked by Seeley,- the 

 Pelorosaurian humerus probably belongs to the same reptile as the 

 Wealden vertebrae named Ornithopsis. The latest large Sauropodous 

 Dinosaur seems, therefore, to have been more slightly built and more 

 active on land than the Cetiosaurus of earlier date. 



III. — On Changes of Level and the Prodtjction of Raised Beaches. 

 By T. F. Jamieson, LL.D., F.G.S. 



I HAVE occasionally drawn attention to the effect produced on the 

 relative level of sea and land by variations of pressure on the 

 surface, such as would be occasioned, for example, by the increase or 

 diminution of the loads of ice which existed during the Glacial period. 

 I argued that the position of the surface must be always tending to 

 an exact equilibrium between the upward and the downward pressure, 

 and that any variation in the superincumbent load must result in some 



1 Phil. Trans., 18.50, p. 379. 



- Quart. Journ. Geol. Soc, vol. xxxviii (1882), p. 371 ; also Geol. Mag., 

 Dec. Ill, Vol. IV (1887), p. 479. 



