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204 



THE EXTINCT BATRACHIA, ItEPTILIA 



on the outef*aspect of the second maxillary. These are not strongly marked, and are separated by concave facets. 

 The basal part of the crown is marked by numerous flue sharp strte, which are most, distinct on the inner face. 



The external face of the maxillary hone presents three series of foramina. These rise superiorly on the premaxil- 

 lary, and increase in number and become irregular on its extremity. 



The ramus of I he mandible is massive, and differs from that of Mosasaurus giganteus in continuing its proportions 

 to its extremity, tts depth at the latter point is as great as the sixth tooth from the front. It is prolonged beyond 

 the first tooth in correspondence with the prolongation of the premaxillary. This extremity is compressed and obtuse; 

 ils inner face is very rugose, as though there had been a closer union at the symphysis than usual, though it would not 

 appear to have been other than ligamentous. The groove for Meckel's cartilage is very large and has been exposed be 

 low the last two teeth, as the splenial terminates at the third. Two series of foramina on the external face of the 

 ramus. There arc alveolse and bases for thirteen teeth on the dentary bono. This, it will be observed, is one more 

 than in M. gracilis, and one less than in other species of Mosasaurus. The posterior extremity of the dentary shows 

 its marks of reception into the notch of the coronoid; it, is more compressed and hiss club-shaped than the correspond- 

 ing part of M. mit.ehillii, and would indicate less lateral flexibility than in some other types. 



The right pterygoid is of less elongate form than in some other species. It presents the sutural face for union 

 with the palatine on the outer anterior extremity, and narrows to an apex a, little in advance. The dentigerous face is 

 widest at the anterior third the length, where the outer margin is expanded. This then contracts and is compressed 

 vertical at the tenth tooth, where it is broken off. The transverse process is given oil' a little anterior to the ninth 

 tooth. The interior face of the, bone is a, vertical plane, without projection, except, a, slight obliquity at the anterior 

 extremity, and if, is dear there has been some interval between this pterygoid and its fellow. The superior margin is 

 obtusely rounded. 



The bases of the. pterygoid teeth are exposed for two-thirds their length, on the outer side of the bone, thus ap- 

 proaching the I'lalecarpus. 'the antero-median are, large, and the, anterior most closely placed. Their crowns are 

 strongly recurved, round in section, and with a, tine sculpture of straight stria', most marked near the base and on the 

 inner side. They are more spaced posteriorly than any other species except M. mitchillii, and are relatively larger than 

 in any except the same species. They have not the compressed form with basal shoulder, characteristic of the M. 

 dekayi. 



Measurement of Muzzle. Inehei. 



Length of fragment, 31. 



" from end muzzle to pre-frontal, 21.5 



" " " " nares, 11.75 



" " " " " maxillary, 5.75 



" " " " " first tooth, 2.5 



Width of muzzle at end, 1.5 



" at anter. extremity nares, 8 



" premaxillary " " " 3.3 



" maxillary betw. 10th and 11th teeth, 3.2 



Depth mandible at extremity, 2.5 



" " " sixth tooth, 3.5 



" pterygoid at transverse process, 2.5 



Width " " " " 1.4 



" " in front,, 2.2 



Length " anterior to transverse process, 7.2 



" crown 5th pterygoid tooth, 1. 



" " 2nd maxillary tooth, 1.9 



Diameter" " " " at base, 1,1 



-4 



The vomers are M usual, separate and narrow. They are in close; contact from the second maxillary to the second 

 premaxillary tooth. Throughout this part of their length they are embraced by posteriorly produced vertical lamina- 



