November 1, 1890.] 



K N O WL EDGE 



245 



secrets aright. When, however, we make this statement 

 we by no means intend to imply that the Megalosaur or 

 any of its immediate kindred were the direct ancestors of 

 birds, but only that they were more or less closely allied 

 to such unknown ancestral types. 



There are almost equally remarkable resemblances in the 

 structure of other parts of the leg of the Megalosaur to 

 that of birds, but the feature indicated is amply sufficient 

 for our present purpose. 



The group of which the Megalosaur is our typical ex- 

 ample is a large one, and contains some species with a 

 thigh-bone upwards of a yard in length, down to tiny little 

 creatures scarcely as large as a rabbit. These reptiles 

 were widely spread over nearly the whole globe ; their 

 remains having been obtained from the secondary rocks of 

 Europe, India, South Africa, North America, and even as 

 far north as Behring Strait. Some of the smaller species, 

 like those found in the lithographic limestones of the 

 Continent and in the United States, probably took con- 

 siderable leaps with their long hind legs, and must thus 

 have resembled the smaller kangaroos of Australia. 



Briefly summing up the result of the foregoing observa- 

 tions, we find thxt the Giant Land Reptiles may be divided 

 into three great primary groups presenting the following 

 distinctive features. In the first group, as represented by 

 the Iguanodon, the teeth were adapted for grinding, and 

 had flattened crowns, ornamented with ridges on the outer 

 side ; the limb-bones were hollow ; the pelvis was bird-like ; 

 and the mode of progression was bipedal. In the second 

 group, as exemplified by the Hoplosaur, we have nearly or 

 quite the largest known land animals ; their teeth were 

 spoon-like, and adapted for vegetable food ; the limb-bones 

 were solid throughout ; the pelvis was not very unlike that 

 of a crocodile ; and the mode of progression was quad- 

 rupedal. Finally, in the third group, of which we took the 

 Megalosaur as our type, the teeth and claws were adapted 

 for capturing and devouring living prey ; and although 

 the pelvis approximated to the crocodilian plan, yet in the 

 structure of the leg and ankle these reptiles (in which the 

 limb-bones were hollow) made a closer approximation to 

 birds than is presented even by the Iguanodon. 



The above-mentioned remarkable variations of structure 

 presented by the members of the three foregoing groups 

 might well have been supposed to exhaust the pecuharities 

 displayed by the Giant Land Reptiles. In the very top- 

 most beds of the secondary rooks of the United States 

 there occur, however, the remains of another group or 

 these creatures, which appear to indicate a special modifi- 

 cation of the original stock from which the Iguanodons 

 took their origin, and which present some of the most 

 bizarre and strange creatures yet revealed to our astonished 

 gaze in a country where fossil animils appear to have run 

 riot as regards strangeness. The occurrence of these 

 creatures in the topmost cretaceous rocks, at a period just 

 before the whole group of Giant Reptiles became extinct 

 for ever, is like the final " ilare-up " at the close of a dis- 

 play of fireworks, and suggests to us that the extreme 

 specialisation to which those creatures had finally attained 

 rendered them unsuitable for the wear and tear of life, and 

 thus conduced to their flnal extinction. 



The reptiles forming this group or sub-group are collec- 

 tively known as the Armoured and the Horned Dinosaurs. 

 Their pelvis is a nndilioation of that of the Iguanodon, 

 uswUly exhibiting the backward dh-ection of the pubis and 

 isL-hium ; but the limb-bones were solid, and either the 

 body was covered with huge bony plates and spines, or 

 long horn-cores, hke those of the oxen, were present on 

 the skull. 



The Armoured Dinosaurs were first made known to us 



'iG. 8. — Side 

 View of the 

 Tooth of an 

 Armed Dino- 

 SAUK. En- 



larged. (After 

 JIarsh.) 



by more or less imperfect skeletons discovered in the Lias, 

 Kimeridge Clay, and Wealden formations of England. 

 One of the best known of these reptiles is the so-called 

 Stegosaur, of which a considerable portion of the skeleton 

 was found some years ago in digging a w-eU in the 

 Kimeridge clay at Swindon ; this specimen being now 

 preserved in the British Natural History Museum at 

 South Kensington. The back of this creature was pro- 

 tected by a number of large spines, but the skull (as is 

 shown by nearly entire skeletons obtained from the 

 Jurassic rocks of the United States) was devoid of 

 horns, and distantly resembled that of the Iguanodon, 

 although more depressed. The teeth of 

 these reptUes resembled the specimen 

 shown in Fig. 8, and were simpler and 

 relatively smaller than those of the Igua- 

 nodon, although constructed on the same 

 fundamental plan. This diminution in 

 the size of the teeth, we may observe in 

 passing, appears to be an instance of that 

 tendency to a reduction or disappearance 

 of the teeth in the speciahsed forms of 

 many groups of animals to which we have 

 alluded in an earlier article. 



The Armoured Dinosaurs were also weU 

 represented in the Wealden (where they 

 were first discovered by Dr. Mantell), 

 although we have at present no e%'idence 

 as to the nature of their skulls. One of 

 these Wealden reptiles, which has been named the 

 Hylffiosaur (from the Greek hiilS, " wood," in allusion to 

 the Wealden, or wooded country), carried a formidable row 

 of large flattened spines forming a crest down the back. 

 The other, termed I'ohjdcdnthus (many-spiued), is remark- 

 able for having had the wdiole region of the loins and 

 haunches protected by a continuous sheet of bony plate- 

 armour, rising into knobs and spines, after the fashion 

 of the carapace of those extinct armadillos known as 

 Glyptodonts.'" 



The earUest evidence of the existence of the Horned 

 Dinosaurs occurs in the greensand of Austria, but the 

 specimens hitherto obtained from these deposits are too 

 imperfect to give us any definite insight into the organi- 

 sation of these reptiles. We accordingly turn to the 

 upmost cretaceous rocks of the United States, where the 

 remains which hive been unearthed must excite the envy 

 of all European paUeontologists. 



As their name implies, one of the most striking features 

 in the organisation of these uncouth monsters is the 

 presence of large horn-cores on the skull, as shown in 

 Fig. 9. The skull of which we give a tigure is remark- 

 able not only for its gigantic size— the length of the 

 figured specimen, which is said to indicate an immature 

 individual, being about six feet — but also for its pecuhar 

 armature and structure. An imperfect skull of another 

 species exceeds these dimensions, huge as they are, and 

 is estimated when entire to have had a length of over 

 eight feet. No other known animals, except wUales, have 

 a skull making any approach to these dnncnsions ; that of 

 the huge Atlautosaur being very small in comparison with 

 the bulk of its owner. The skull before us is likewise 

 remarkable for its wedge-like form when viewed from 

 above, and carries a pair of large horn-cores immediately 

 over the eyes, and a short and single core above the nose. 

 During life it may be inferred with a Jiigh degree of 

 probability that these bony cores were sheathed with horn, 



* Spo the article on Muil-Clad Animals in Knowledge for November 



lS8il. 



