30 Colossal Basilosaurus. 



sides are slightly concave in the middle, and the weight of the 

 vertebra is forty-four pounds. Allowing the individual to 

 possess as many vertebras as the Plesiosaurus, that is to say, 

 sixty-six, independent of those of the tail, the weight of the 

 whole fossil skeleton may be fairly estimated as exceeding two 

 tons, even supposing each vertebra to weigh only thirty pounds 

 instead of forty-four, and calculating the weight of the extre- 

 mities, pelvis, and tail, to be collectively but a little heavier than 

 the spine alone. 



Judging from the position and descending obliquity of the 

 transverse apophyses, and the small size of the canal for the 

 spinal marrow, this vertebra must be referred to the posterior 

 part of the column, and most probably to the lumbar region. 

 This opinion is strengthened by the coalition of the two fora- 

 mina or fossae, which characterize the inferior aspect of the ver- 

 tebrae of the posterior part of the column in the spiral bones of 

 the Plesiosaurus, in which respect these portions of the two 

 fossils closely resemble each other ; they are also similar in the 

 form of the planes of the articulating surfaces of the bodies of 

 the vertebrae. But our fossil differs totally from the same por- 

 tion of the Plesiosaurvis in its proportions, the vertebrae of the 

 latter being broader than long. All the superior apophyses of 

 the Plesiosaurus are attached by suture to their bodies, but 

 there are no marks of such a structure in our fossil. 



Judging from relative proportions, the Megalosaurus did not 

 attain to more than thirty or forty feet in length. The Igua- 

 nodon of Mr Mantel did not exceed sixty feet, but the indivi- 

 dual now indicated could not have been less than from eighty 

 to a hundred feet. According to the statement of Judge Bry, 

 to whom the society is indebted for the specimens, they were 

 four hundred feet in extent, nearly in a curvilinear direction 

 marked by these fossils in the soil, which we must presume in- 

 cluded the remains of several individuals. If future discoveries 

 of remaining portions of this skeleton should confirm the indi- 

 cations above pointed out, we may suppose the genus to which 

 it belonged will take the name, not inappropriately, of Basilo- 

 saurus. 



Locality. — Banks of the Washita, Louisiana. 



