NATURAL HISTORY OF THE PRIMEVAL WORLD. 



23 



curtailed in the paltry climbing and leaping reptile 

 wliicli lived iu tlie Jurassic period. Among existing 

 animals only a single reptile has been found supplied 

 with wings, or digital appendages analogous to the 

 merabraniferous wings of the bats, and bearing a faint 

 resemblance to the Pterodactyle. This is called the 

 Dragon, or Draconidcc, a family of Saurians, hereafter 

 described, distinguished by the first six ribs, instead of 

 circling the abdomen, extending in nearly a straight 

 line, and sustaining a prolongation of skin which forms 

 a kind of wing like that of the Pterodactyle. Without 

 assistance from the four feet, tliis wing sustains the 

 animal like a parachute, as it leaps from branch to 

 branch ; but tlie creature has no power to beat the air 

 witli it as birds do during their aerial fliglits. 



Returning to our general survey of the animal life of 

 the Lias, we notice that in its strata fully two hundred 

 and forty-tliree genera, and four hundred and sixly- 

 seven species of zoophytes and molluscs have been 

 discovered. Among the former we may particularize 

 Asterias lumhricalis and Pakcocoma Furslcinhcrf/ii as 

 constituting a genus not unlike the Star-fislies {Riuliata) 

 of existing seas. The Encrinites were replaced 

 by other species of the same genus, the Aslro- 

 pccten, the Amphiwa, and the OpJiiodenna. 

 Aimelids, like the Serpula; barnacles, or Pol- 

 Ucqxs; bivalveciustaceans, suchas the Cypris, 

 Cyprkkci, and Esthcria ; and the higher Crus- 

 tacea, E?'yon, Mcfjacheirua, and Glyplava, 

 were also abundant. The molluscan genera 

 included the delicate polyzoans, or sea-mats, 

 such as Caiopora and Diastopora; the deep- 

 sea bracliiopods, TcTcbratula, Spiri/cra, and 

 Discoria; and some species of tlie oyster 

 (Ostrca), which now first made its appearance. 

 The sea-shores were tlnonged with tlio gas- 

 teropods, Truchus, Turbo, P leurotomarin, and the like. 

 Legions of belemnites and ammonites, also, swarmed 

 in the warm waters of the Oolitic ocean. 



Tliat ocean also contained a great number of the 

 fislios called Ganoids; that is to say, with hard glit- 

 tering scales. One of the largest species was the Le- 

 pidoltis gigas. We frequently meet with the teeth of 

 the Acrodus nohilis, populaily known by the name of 

 " fossil leeches," but never with its entire skeleton. 

 The same is the case with the Hijhodus reticulatus. 

 The bony spines forming the anterior part of the dorsal 

 fin of this fish, had long attracted the curious attention 

 of geologists before their true character was ascertained, 

 and had received the distinguishing appellation of Ich- 

 thyodvndites. By some naturalists they are conjectured 

 to be the jaw of an animal ; by others, the weapons, 

 offensive and defensive, of a genus resembling tlie living 

 Silarus or BalUtcs; but Agassiz has satisfactorily de- 

 monstrated that they were the bonj' spines of the fin, 

 as in our modern genera ol Astraceins and Chhnccraa, 

 where the fin's concave face is similarly armed. The 

 spines were simply embedded in the flesh, and attached 

 by strong muscles, serving, as in the Chimara, to 

 raise or depress the fin ; their action resembling that 

 of a movable mast lowering backward. 



But we must not omit a few details in reference 

 to the gigantic land Saurians of the Oolitic era — the 



Megalosaurtis, Hyhvosaiirus, and lyiuinodon; or the 

 insectivorous quadrupeds — tlie Amp/nthcriiim, P/ias- 

 culutherlum, Stereognalhus, Trionodon, and Phigian- 

 lax, which have been exhumed in the upper Oulitic 

 formation. 



The Mcgalosauriis,* or Great Lizard, was a terres- 

 trial saurian, about forty feet in length. It seems to 

 liave combined many of the characters both of the 

 iguana and the monitor ; the latter a lacertian reptile 

 wliicli flourishes in tropical India and on the banks of 

 the Nile. That it was carnivorous in its habits is 

 evident from the complicated structure and arrange- 

 ment of its teeth, which may be described as a com- 

 pound of the knil'e, the sabre, and the saw. 



" Wlien first protruded above the gum, the apex of 

 eacli tooth presented a double cutting edge of serrated 

 enamel. In this stage its position and line of action 

 were nearly vertical, and its form like that of the two- 

 edged point of a sabre, cutting equally on each side. 

 As the tooth advanced iu growtli, it became curved 

 backwards, in the form of a pruning knife, and the edge 

 of serrated enamel was continued downwards to tiio 



Jaw of the Megalosaurns. 



base of the inner and cutting side of the tooth ; whilst, 

 on the outer side, a similar tdge descended, but to a 

 short distance from the point, and tlic convex portion 

 of the tooth became blunt and thick, as the back of a 

 knife is made thick, for the purpose of producing 

 strength. The strength of the tooth was further 

 increased by the expansion of its sides. Had the ser- 

 rature continued along the whole of the blunt and 

 convex portion of the tooth, it would, in this position, 

 have possessed no useful cutting power; it ceased pre- 

 cisely at the point beyond which it conld no longer be 

 effective. In a tooth thus formed for cutting along its 

 concave cdgp, each movement of the jaw combined 

 the power of the knife and saw ; whilst the apex, in 

 making the first incision, acted like the two-edged point 

 of a sabre. The backward curvature of the full-grown 

 teeth enabled them to retain, like barbs, the prey which 

 they had penetrated. In these adaptations we see 

 contrivances which human ingenuity has also adopted 

 in the preparation of various instruments of art." 



We have hitherto been treating of carnivorous rep- 

 tiles; but there were species of the same great family, 

 in the Oolitic period, which assumed the character and 

 office of Ilerbivora. Such was the Iguanodon, whose 

 fossil remains were first discovered by Dr. Mantell in 

 the Wealden fresh-water deposits of Tilgate Forest, 

 * Fioni fi-^yaXos, great, and ^aw^af, lizard. 



