OOLITIC DINOSAURS. 593 



18 inches, " a part, apparently a small one, being wanting from both extremities " of the 

 iliac bone. But, on this basis, we may allow to the ilium of 45 inches length a 

 sacrum of 24 inches, or one of four vertebras, each G inches in length. It is not 

 probable that a saurian with iliac bones between 3 and 4 feet in length, and thigh-bones 

 between 5 and 6 feet in length, would have a sacrum reduced to the crocodilian formula 

 of two vertebrae. 



Admitting, then, that more numerous sacrals, such as the Tortoises show, are not 

 the sole and may not be the chief character of Dinosauria, and that the generalisation 

 signified by that term is a passing one, denoting a step in the progress of knowledge of 

 the extinct Beptilia ; and supposing that it should be now limited to saurian genera, 

 combining, with four or more sacrals, the alternating or interlocking arrangement of the 

 autogenous vertebral elements — as in Bofhriospond/jlus, Megahsaurus, lyuunodoii, Hylteo- 

 sauriis, Oniosaurus — the question to be solved is : — " Does such arrangement characterise 

 the sacrum of Cetiosaurus ? " Have we, in the absence of any certain or definite knowledge 

 of the cranial and dental characters of the genus, grounds for determining its ordinal 

 relations to the Dinosaurs, Crocodiles, Sauropterygians, Ichthyopterygians, Lacertians, 

 &c. ? I am disposed to wait for such additional evidence, admitting, meanwhile, the 

 faculty of terrestrial progression in a superior degree to that of the amphibious Crocodiles; 

 nevertheless, the habitual element of the Cetiosaur may have been, and I believe to have 

 been, the waters of a sea or estuary. And I may here repeat the remark on the initial 

 evidence of the species : — " The main organ of swimming is shown, by the strength and 

 texture and vertical compression of the caudal vertebrae, to have been a broad vertical 

 tail ; and the webbed feet, probably, were used only partially, in regulating the course of 

 the swimmer, as in the puny Amhlyrhynclms of the Galapagos Islands, the sole known 

 example of a saurian of marine habits at the present period."* 



In fact, to the characters of the caudal vertebrae of Cetiosaurus longus known to me at the 

 date of the above-quoted ' Report,' viz. — " post-zygapophyses represented by hollow pits," 

 " slight concavity of both articular ends of the centrum, moderate compression of the sides 

 between the expanded ends, which are subcircular,t the under surface concave lengthwise, 

 marked by parial articular surfaces, showing the haemal arches to be articulate therewith 

 over the vertebral interspaces"t — the discovery of the grand proportion of the skeleton of the 

 individual at the Enslow quarries adds a demonstration that the haemal arch in an anterior 

 caudal vertebra (fig. 11) attained a length of 1 foot 2 inches; and that the neural spine 

 "probably rose twelve inches above the canal/'§ giving a total vertical extent of upwards 

 of a yard to such anterior caudal. The vertebrte probably exceeded in this dimension 

 at the middle of the tail. 



The modifications of the caudal vertebrae in parts of the tail of Cetiosaurus longus, 

 as exemplified by specimens from the Great Oolite described and figured by Phillips 

 (' Geology of Oxford,' 8vo, 1871), are similar to those in the instructively preserved 

 * 'Report,' &e., p. 102. f lb., pp. 101, 102. t ' I''-,' &c., pp. 101, 102. § Phillips, op. cit., p. 259. 



