No. I.] THE SKULL /iV THE MOSASAURID.E. 9 



separated from the quadrates by intervening bones ; but on both 

 points he was in error." They are "attached posteriorly to 

 the quadrates by ligament, to the basipterygoid processes in 

 the same way, to the maxillaries by the intervention of a dis- 

 tinct transverse bone, and to the true palatines by squamous 

 suture." — "The true palatines are small edentulous bones, in 

 front and outside the pterygoids. They separate the latter from 

 the slender, distinct vomers." — "In none of the genera were 

 the pterygoids united by suture on the median line, but were 

 more or less widely separated. 



"The new characters above presented are all Lacertilian, 

 rather than Ophidian. The important characters of the Mosa- 

 sauroids now known indicate that they form a sub-order of the 

 Lacertilia, which should be called Mosasaiwia." 



Dollo, 1 882-1 890. 



Dollo has published quite a number of papers on the mor- 

 phology of the Mosasauridae. 



In his first note, printed in 1882,^ he describes a complete 

 naso-premaxillary of the typical Mosasaurus ; but he is inclined 

 to consider this element as the premaxillary alone, — a view 

 which is incorrect, since all Mosasauridae have the nasals co- 

 ossified with the premaxillaries. The true nature of the ptery- 

 goids in the type of Mosasaurus is recognized, and their 

 complete distinctness from each other admitted. 



Mosasaurus Maxiiniliani is made the type of a new genus, 

 Pterycollasaiirus, on the belief that the pterygoids in this form 

 are united in the middle line. There is not the slightest doubt, 

 however, that these elements are simply crushed together, and 

 that they are really separated from each other as in all Mosa- 

 sauridae. The genus Pterycollasaiiriis is therefore not admitted. 

 Another new genus, Plioplatccarpiis, is established. The prin- 

 cipal character of this genus consists in the presence of a 

 "sacrum." In a later paper ^ this genus is elevated on this 

 account to the rank of a special family, Plioplatecarpidas. Other 



1 Dollo, L., N^otc sur Vosteologie des MosasaiiridcB, Bull. Mus. Roy. Hist. Nat. 

 Belg., Vol. I, pp. 55-74, pis. iv-vi. 



2 Dollo, L., Notes d" Osteologie erpetologiqiie, Ann. Soc. Scient. Bruselles, 1S85, 

 P- 335- 



