June, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



129 



and were long and peg-like; as worn out they were 

 replaced in constant succession. The manner of this 

 replacement is indicated in Fig. i, which shows a sec- 

 tion through the upper jaw. 



It has been suggested that this monster was largeb' 

 aquatic in its habits, partly on account of its enormous 

 bulk, and partly because of the position of the nostrils. 

 These opened, not at the end of the snout, but in the 

 form of a large hole between the eyes — the white shield 

 in the front of the skull in the photograph. There can 

 be little room for doubt, indeed, but that the peculiar 

 position of these apertures represents an adaptation to 

 an aquatic habitat. Probably Diplodocus, like the 

 modern hippopotamus, passed most of its time sub- 

 merged in rivers, and thrust the head out of the water 



ing. It seems more probable that the Dinosaurs were 

 viviparous. 



A more plausible hypothesis as to the causes 

 of extinction of Dinosaurs, and other animals which 

 have attained huge proportions, is that of Dr. C. W. 

 Andrews. " An almost necessary corollary," he re- 

 marks, " of this increase in bulk, is . . . the lengthening 

 of the time taken to attain sexual maturity .... A 

 necessary consequence of the longer individual life 

 will be that in a given period fewer generations will 

 succeed one another, and the rate of evolution of the 

 stock will, therefore, be lowered in the same propor- 

 tion. If, now, the conditions of life undergo change, 

 the question whether a given group of animals will sur- 

 vive or become extinct, will depend upon whether it 



Replica of Diplodocus, (Fmm the l 



at intervals, just far enough to enable breathing to take 

 place. Here it lived upon succulent vegetation, which 

 was torn up by the rake-like teeth. 



The causes which led to the extinction of this 

 monster, and of others of like kind, will always remain 

 a mystery. These leviathans represent the high- 

 water mark attained by the reptiles, and it is 

 significant to note that they disappeared just as 

 the mammals were entering the arena of life. The 

 late Prof. Cope, indeed, suggested that these early 

 mammals (Jurassic) played no small part in the over- 

 throw of their giant neighbours; that beasts of the size 

 of the shrew and hedgehog hunted out the nests of 

 these colossal creatures and gnawing through the shells 

 of the eggs, destroyed the young. This explanation 

 savours rather of wild conjecture than scientific reason<- 



giiialin tilt: Cai-negie Miiicum at i'l/tshuii;.} 



can undergo sufficiently rapid variation to enable it to 

 avoid getting so far out of harmony with its surround- 

 ings that further existence becomes impossible. ..." 

 Finally, it may be well to remind our readers that 

 the great American continent has by no means the 

 monopoly of these titanic Dinosaurian beasts. In the 

 British Aluseum, for example, there may be seen the 

 limbs of an enormous Dinosaur known as Cetiosaurius, 

 obtained some years ago in Oxford. This creature 

 must have rivalled Diplodocus in size. The Great 

 Iguanodon, again, which once roamed over our islands, 

 might well have disputed the right of way with Diplo- 

 docus, inasmuch as it stood some i8 feet high, and had 

 the fore limbs armed with powerful spurs. But of 

 these, and others, we may have more to say on another 

 occasion. 



