202 BRITISH FOSSIL REPTILES. 



no other teeth have as yet been found in the Cretaceous Series to which the fossils in 

 question could be referred. These are at present, however, the chief grounds of the 

 probability that such teeth and bones of a large Saurian, may have belonged to the 

 same genus. 



The bones about to be described, are unquestionably the remains of a Saurian of 

 marine habits, but most probably of the Crocodihan order, as gigantic as the 

 Cetiosaurus or Poli/pfi/chodon, but, in the absence of any associated parts yielding the 

 dental and vertebral characters, not certainly referable to any known genus. They 

 were discovered, in 1840, by H. B. Mackeson, Esq., of Hythe, in the Green- sand 

 Quarries, near that town, and include portions of the coracoid, humerus, and ulna, of 

 the iliac, ischial, and pubic bones, a large proportion of the shaft of a femur, parts of 

 a tibia and fibula, and several metatarsal bones, four of which exhibit their proximal 

 articular surfaces. The remains occupied a space in the quarry, of about fifteen feet 

 by twelve, where it would seem that a proportion of the skeleton of this gigantic 

 Saurian, including the pelvis with one hinder extremity, and a part of the fore-limb 

 had been exposed. In consequence of the absence of vertebrae and teeth, the present 

 observations will be limited to indicating the characters by which these remains differ 

 from previously known extinct genera of Saurians. In the first place, as the femur 

 and other long bones have no medullary cavities, but a central structure composed of 

 coarse cancelli, it is evident that the animal of which they formed part was of marine 

 habits, and did not belong to the Binosauria ; but the best-preserved bone being a 

 femur, this circumstance, independently of the size and shape of the metatarsals, at 

 once negatives the idea that these remains belonged to the Cetacean order, whilst the 

 form and proportions of the metatarsals equally forbid their reference to any other 

 Mammalian genus, or to the Reptilian order Enaliosauria. The cells of the cancellous 

 tissue are about a line in diameter : the compact outer crust or wall of the bone is 

 from four to five lines in thickness. In the recent state, the cells of the cancellous 

 structure of the marine Saurian's bones were doubtless filled with a fluid oil, as in 

 the similarly coarsely cancellous bones of the Cetaceans, and thus the specific gravity 

 of the animal would be nearly accommodated to that of the fluid in which it 

 principally, if not exclusively existed. 



Femur. — The portions of this bone, PI. 27, fig. 1, secured by Mr. INIackeson 

 include about the two distal thirds, excepting the articular extremity ; its length is 

 2 feet 4 inches ; its circumference in the middle, or smallest part of the shaft, is 

 1 5 inches 6 lines, and at the broken distal end, 2 feet 5 inches. These dimensions 

 prove that the animal was equal to the most gigantic described Iguamdon* If the 

 supposition of the proportion of the femur which has been preserved be right, this 

 bone differs from that of the Iguanodon, not only in the want of a medullary cavity, 



* The length of the largest femur yet obtained of this Saurian is 4 feet 6 inches, its smaller 

 circumference 1 foot U) inches. 



