. The Quarterly journal of the Geological Society of London. on of Lacertians on the one hand with Crocodilia and Chelonia,and with Ophidia on the other hand, is the greater tendency in certainsutures to mark off an anterior half of the ramus, including thedentary, and splenial, from the posterior half; with this modi-fication, that in the Iguanians (fig. 19) the coronoid piece, si, wouldgo with the anterior division, and in the Monitors (fig. 20) withthe posterior one. The subvertical suture in Amblyrhynchus (fig. 19, s-s) runs fromabove downward, first between the surangular, 31, and coronoi
. The Quarterly journal of the Geological Society of London. on of Lacertians on the one hand with Crocodilia and Chelonia,and with Ophidia on the other hand, is the greater tendency in certainsutures to mark off an anterior half of the ramus, including thedentary, and splenial, from the posterior half; with this modi-fication, that in the Iguanians (fig. 19) the coronoid piece, si, wouldgo with the anterior division, and in the Monitors (fig. 20) withthe posterior one. The subvertical suture in Amblyrhynchus (fig. 19, s-s) runs fromabove downward, first between the surangular, 31, and coronoid, 31;then between the surangular and the combined splenial 33, anddentary, 32. In the Monitor ( Varanus niloticus) (fig. 20) the subvertical suture,s-s, runs, first between the surangular, 31, and the dentary, 32; thenbetween the angular, 30, and the combined dentary and small part of the fore end of the coronoid, 31, supplements theupper end of this subvertical suture. In the Mosasaurus (fig. 18) this subvertical division, s s, of the Fig. Mosasaurus. ramus follows more closely the pattern of the Monitor than of theIguanians. The chief modification is the formation of the lowerpart of the suture by the angular, 30, and splenial, 33, exclusive of THE KEPTILIAN CLASS OF THE MOSASAUKID^. 701 the dentary, 32 ; but this unites with the surangular, 31, and a smallpart of the coronoid, 31, as in the Monitors. In all these Lacertiansthe increasing thickness of the ramus toward its lower borderaugments the breadth of that part of the subvertical suture. Butthe sutural line, s s, in each instance describes a more or lesszigzag or angular course, impeding transverse yielding or move-ment of the fore upon the hind half of the ramus. Definition of the constituent elements is clear in the perfectmandibles of Mosasaurus Hoffmanni and M. Maximiliani, in whichlatter they bear the Cuvierian letters in Prof. Goldfusss mono-graph*. In the least-mutilated of the subsequently disco
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
