24 



NATURAL HISTORY OF THE PRIMEVAL WORLD. 



Sussex. From the similar construction of the teeth of 

 this ancient genus with that of the teeth of the modern 

 iguana, there can be no doubt of their near connection. 

 But while the iguana rarely exceeds five feet in length, 

 its congener of the Oolitic period must have been 

 nearly five times as long. Its thigh-bone exceeded in 

 bulk that of the largest elephant! Presenting a circum- 

 ference of twenty-two inches in its smallest part, its 

 entire length must have been between four and five 

 feet. If we compare the proportions of this colossal 

 bone with those of the animal's fossil teeth, we find that 

 they bear to one another nearly the same ratio which 

 the femur of the iguana bears to its similarly-con- 

 structed and peculiar teeth. We thus obtain a stand- 

 ard of comparison which justifies us in estimating the 

 dimensions of the lyuanodon as follows* : 



Length from snout to extremity of the tail, . 70 feet. 



Length of tail, 6'2| " 



Circumference of body, 1-JJ; " 



The teeth of the Iguanodon were not lodged in dis- 

 tinct sockets, like those of crocodiles, but fixed, like 

 those of lizards, along the internal face of the dental 

 bone, to which they adhered by one side of the bony 

 substance of their root. 



As the reptile fed upon tough vegetable food, its 

 teeth were admirably fitted for this purpose by their 

 cutting edges, form of curvature, and points of enlarge- 

 ment and contraction. They were each furnished with 

 a sharp serrated edge, extending on either side down- 

 wards to the broadest portion of the body of the tooth, 

 and thus preserving its utility until worn down to the 

 very stump. To compensate for the gradual destruc- 

 tion of this serrated edge, a plate of thin enamel was 

 placed on the front of the tooth. As the softer mate- 

 rial of the tooth itself must have worn away more readily 

 than this enamel, and most readily at the part remotest 

 from it, an oblique section of the crown was constantly 

 maintained with a keen-cutting front edge, not unlike 

 (if the reader will permit the comparison) that of a pair 

 of strong iron pincers, or nippers. 



The structure of the skeleton is remarkable. The 

 head, it is evident, must have been produced into a 

 short snout, supporting a nasal horn. The vertebral 

 column in some respects might be compared to that of 

 a fish, but was distinguished from it by its lofty mural 

 arches. The sacrum, wholly unlike that of any other 

 reptile, consisted of five anchylosed joints. The body 

 did not creep upon the ground, but was raised above it 

 by long and robust limbs ; each terminating in a three- 

 toed foot, about twenty-one to twenty-four inches in 

 height, and nine and-a-half to ten inches in breadth. 

 The huge tridactyle impressions discovered in the argil- 

 laceous Wealden beds, and long supposed to have been 

 produced by some colossal bird, are considered by some 

 geologists to be the footprints of the Iguanodon. Pro- 

 fessor Huxley has recently sought to prove, and with 

 considerable success, that they were produced by the 

 Pterodactyle. 



Another large and singular Oolitic reptile, found in 



* Professor Owen, however, disputes these conclusions, and 

 places the entire length of the lyuanodon at nut above twenty- 

 eight feet. 



the Wealden strata of Kent and Sussex, has been named 

 the Hylccosaurus, or Forest-lizard. From the frag- 

 ments exhumed at different times, and in different 

 localities, we gather that it was herbivorous in its 

 habits; with a broad long body, terminating in a long, 

 flexible, slender tail, and resting on short but solid 

 limbs ; a tuberculated and scaly skin ; small, close-set 

 teeth ; and a ridge, or crest, along the back, of thin 

 angular, bony spines. This dermal fringe reminds the 

 naturalist of the horny crest on the back of the iguana. 

 They varied in height from five to seventeen inches, 

 and in width from three to seven and-a-half inches at 

 their base. 



This extraordinary lizard was probably about twenty- 

 five feet long. Only one species has been discovered, 

 which is known by the scientific appellation of llylcno- 

 saurus Oweni. 



Contemporary with these strange reptilian forms were 

 certain mammals of a peculiar type, as, for instance, 

 the Amphitherium, which is supposed to be the most 

 ancient representative of its order on the globe. Cuvier 

 first determined, from the examination of the jaw of a 

 fossil specimen, that it was a marsupial ; whence another 

 French naturalist proposed to call it Thylacoihcrium, 

 or Pouched Wild-beast, while Phascolutheriuin was 

 also suggested as a suitable designation. Its present 

 name, given by Blainville, has been adopted by Pro- 

 fessor Owen, and, on his authority, by most English 

 writers. From the structure of its teeth it would seem 

 to have lived upon insects ; and remains of beetles occur 

 in the Oolitic slate of the Stouesfield quarries, where it 

 was first discovered. 



Two species of this interesting mammal have been 

 distinguished. 



The Phascolotherium is now acknowledged as a dis- 

 tinct genus, whose fossil relics were also first found, like 

 those of the Amphiiherium, in the Stonesfield quarries 

 of Oxfordshire. It is only known by the jaw, pre- 

 served in the British Museum, but was undoubtedly a 

 marsupial animal, and in structure and habits closely 

 analogous to the living marsupials of Australia. 



Before quitting the Oolitic strata we must refer to its 

 remains of Fishes, Molluscs, and Zoophytes. 



Among the Fishes the predominant types were the 

 Ganoids and Ophiopsis. Among the Ammonites we 

 meet with Ammonites, Humphry sianus, A. lullatns, 

 A. Brongniartii, Nautilus, lineatus, and many other 

 representatives of the Cephalopods. Tercbrotulce still 

 flourished, and among Gasteropods the Pleurotomaria 

 conoided was remarkable for the elegance of its shape 

 and the variety of its markings. Among the Acephala 

 were the Ostrea Marshii and Lima j^roboscidea, and 

 the species of molluscous Polyzoa were as numerous as 

 they were beautiful. Echinoderms and Polyps swarmed 

 in the warm genial seas ; most noticeable among the 

 latter, the Eunomia radiata. 



This strange zoophyte is found in great masses many 

 feet, nay, yards in circumference ; each mass containing 

 myriads of the animal, and implying a long series of 

 years to account for its formation. The Eunomia 

 lived under the waters, but only at a comparatively 

 small depth below their surface, and in this position 

 accumulated large far-stretching banks and entire islets, 



