CRETACEOUS FORMATIONS. 35 



comes from a more posterior position of the spine than that represented in fig. 3. 

 Fig. 5 gives a view of a caudal vertebra, which demonstrates another Mosasaurian 

 character in the anchylosis of the haemapophyses or chevron-bones to the centrum, 

 as in the posterior caudal vertebrae of Mosasaurus Hoffmanni ; but the haemal canal 

 (fig. 4, e) is relatively wider, and the entire centrum is much longer than in the 

 corresponding kind of vertebra figured by Cuvier* or by Faujas St. Fond.f 



Three views of the body of a vertebra of the Mosasaurus gracilis, discovered 

 by the Rev. H. Hooper, M.A., distinguished by his geological researches in the 

 neighbourhood of Lewes and Brighton, are given in Mr. Dixon's work above cited, 

 Tab. XXXIX, figs. 5, 6, & 7. This specimen is from the Sotheram Chalk-pit, near 

 Lewes. 



From the genus Leiodon% (T. IKA, fig. 5**) the Mosasaurus gracilis (lb. fig. 9) 

 differs, like the Mosasaurus Hoffmanni (lb. fig. 7), in the inequality of the two sides 

 of the crown of the teeth, which are bounded or divided by the anterior and posterior 

 ridges. The Mosasaurus Maximiliani (lb. fig. 8) differs from the genus Leiodon in the 

 polygonal character of the crowns of the teeth. 



The interest which must be excited in the Naturalist and Palaeontologist by an 

 extinct Saurian, essentially organised according to the Lacertian type, but developed 

 on a scale surpassing that of the largest existing Crocodiles, and especially modified, 

 as it seems, for aquatic life, leads me to believe, that any additional facts tending to 

 complete its restoration will here be acceptable, although they may not have been 

 afforded by fossils from British strata. In the formations of the Cretaceous Period 

 in North America, answering in mineralogical characters to our Green-sands, though 

 probably contemporaneous with the newest chalk deposits of Europe, many fine 

 examples of Mosasaurus, of the species called by Goldfuss, Mos. Maximiliani, have 

 been found, and the discovery affords a highly instructive instance of the coexistence 

 of particular forms of fossil Reptilia in remote parts of the earth, at the same 

 geological epoch. In a series of remains of the Mosasaurus Maximiliani, from a 

 Green-sand formation at New Jersey, United States, kindly submitted to my examina- 

 tion by Professor Henry Rogers, of Pennsylvania, I detected the basioccipital bone 

 of the cranium, which gave additional evidence of the Lacertian affinities of the 

 Mosasaurus, and new proof of the Cuvierian law of correlation of organic structures. 

 This basioccipital bone, which is figured in the ' Quarterly Journal of the Geological 

 Society,' November, 1849, pi. x, fig. 5, was three inches and a half in length, 

 and four inches nine lines in extreme breadth. It resembled the centrum of the 

 " vertebra dentata" of the Crocodilia, in being convex behind and flattened in 

 front. The convexity formed the inferior and major part of the occipital condyle, 

 which must have been reniform, the angles being superior, and formed by the 



* Cuvier, loc. cit., pi. xix, fig. 6, A, B. t Loc. cit, pi. viii. 



% Odontography, 4to, p. 261, pi. 72, figs. 1 aud 2. 



