SAUROPTERYGIA 217 



maxillary series are supported in a marginal row of alveoli by 

 the premaxillary and maxillary bones ; the palatal series are 

 implanted in the palatine and pterygoid bones. The maxillo- 

 premaxillary teeth are five in number on each side, two 

 implanted in the premaxillary, and three in the maxillary. 

 The premaxillary teeth are subequal, smaller than the maxillary 

 teeth ; their crowns are subhemispheric in P. laticeps, but in 

 P. Andriani they present a bent, pointed, prehensile character. 

 In P. laticeps the first maxillary tooth has a full oval crown, 

 4i lines by 4 in diameter ; the second measures 5i lines by 

 4i lines in diameter ; the third is subcircular, 8 lines in 

 diameter, on the right side. The palatal series begins on the 

 inner side of this tooth, and consists of two teeth on each side. 

 The first tooth has a full elliptical crown, 10 lines by 8 ; the 

 second tooth, developed in the broad pterygoid bone, presents 

 a full oval shape, 1 inch 9 lines by 1 inch 3 lines in diameter. 

 In Placodus gigas and P. Andriani the palatal teeth, three in 

 number on each side, are all of large size, slightly increasing 

 from before backwards ; they are situated close together, 

 forming on each side a series a little curved with the convexity 

 outwards, and the interspace between the two series is very 

 narrow. The first tooth is triangular, the second and third 

 are quadrangular ; each with the angles rounded, and the 

 transverse diameter exceeding the fore and aft or longitudinal 

 one. The maxillary teeth are much smaller than the palatal 

 ones, have a rounded or subquadrate crown, are four in num- 

 ber, and of subequal dimensions. The premaxillary teeth, 

 three in number on each side, are more remote and distinct 

 from the maxillary teeth than in Placodus rostratus and P. 

 laticeps ; their crowns are more elongated and conical than in 

 P. laticeps ; the prehensile power of the prolonged premaxil- 

 lary part of the jaw being obviously greater in Placodus gigas 

 than in P. laticeps or P. rostratus. The size of the last tooth 

 in P. laticeps surpasses that of any of the teeth in the previ- 



