MOSASAURUS. 33 



most important remains, comprising the greater part of a skeleton, consisting of a 

 nearly entire skull and eighty-seven vertebras, were found, by Major O'Fallon, on 

 the Upper Missouri, in the vicinity of Big Bend, and were presented by him to 

 Maximilian, Prince of Wied, who was then travelling in America. Conveyed to 

 Europe, the remains were presented by the Prince to the Museum of the Academy 

 of Naturalists of Bonn, and were described in the Transactions of the Academy by 

 Dr. August Goldfuss.^ 



Cuvier views the skull of the great Maestricht Mosasaurus as intermediate in 

 anatomical characters to that of the existing Monitor and Iguana} The length of 

 the lower jaw he gives as three feet nine inches,^ and estimates the skull to have 

 been nearly four feet.* On each side of the lower jaw there are fourteen teeth f 

 to the upper maxillary bone eleven teeth, and as it is estimated that there may have 

 been three additional teeth to each side of the inter-maxiUary bone, the number 

 would be the same in the upper as in the lower jaw.^ The pterygoids, as in the 

 Iguana, also possess teeth, of which Cuvier states there were eight to each bone.' 



The skull of the Missouri Mosasaurus is about half the length of that of the 

 Maestricht Mosasaurus, but Dr. Goldfuss assumes too much when he says the com- 

 plete ossification of all parts, as well as the frequently perceptible solidification of 

 the teeth, prove that the individual had reached maturity,^ for the skull and teeth 

 of Saurians exhibit the same characters of ossification and development from youth 

 to extreme age. As remarked by Owen, " the characters of immaturity are not 

 manifested by the cold-blooded animals in their osseous and dental systems as they 

 are in the warm-blooded and higher organized mammalia."" 



In the jaws of the Missouri Mosasaurus there are the remains of eleven teeth 

 above and below, and supposing three more to have existed in the anterior extremi- 

 ties of the jaws, which were lost, the number would be equal to that of the Mae- 

 stricht Mosasaurus. The pterygoid bones, according to Dr. Goldfuss, are each 

 occupied with the remains of ten teeth, being two more than the number mentioned 

 by Cuvier as existing in the Maestricht skull. 



The vertebrae of Mosasaurus have their bodies concave in front and convex behind. 

 Cuvier^° estimates the number to have been about one hundred and thirty-three. 

 These he divides as follows : The atlas and axis ; eleven vertebrae of the neck and 

 thorax distinguished by the presence of an inferior apophysis or hypapophysis 

 together with articular and transverse processes ; five similar vertebrae without the 



vertdbra, represented in Fig. 34ffl, referred to Macrosaurus, the tooth,. represented in Fig. 39, referred 

 to Pohjplychodon rugosus, and that represented in Figs. 45, 46, which I referred to a reptile of un- 

 known relation with the name of Drepanodon ivipar, I also suspect to belong to Mosasaurus. 



* Schildelbau des Mosasaurus. Nov. Act. Acad. C. L. C. Nat. Cur., Yol. XXI, p. 1T3. 



» Ossem. Foss., Ed. 4, T. 10, p. 150. ' Ibid., p. 168. ♦ Ibid., p. 151. 



= Ibid., p. 139. " Ibid., p. 143. ' Ibid., p. 148. 



* " Die vollstiindige Verknocherung aller Theile, so wie die haufig bemerkbare Ausfiillung der 

 Ziihne beweisen, dass das Individuum seine vollstandige Ausbildung erreicht hatte." Schadelbau 

 des Mosasaurus, Nov. Act. Acad. C. L. C. Nat. Cur., Vol. XXI, p. HT. 



" British Fossil Reptiles, p. 187. " Ossem. Foss., T. 10, p. 165. 



5 April, 1865. 



