OOLITIC DINOSAURS. 625 



into bone, the central part may be alisorbed and marrow be substituted for bone. Then, 

 in the course of fossihsation matrix or spar may be substituted for marrow. Or the 

 absorption of previous solid bone, such as that of a chelonian humerus or femur, may go 

 further ; the marrow may also be absorbed, the wall of the bone may be perforated, or 

 ' tapped,' and air be admitted from a contiguous portion of lung. But in the course of 

 fossilisation the non-ossified parts of the substance of the bone become filled by the 

 same mineral infiltration whether the cavities in the recent state contained chondrine, 

 marrow, or air. 



The inconsiderate conclusion that fossil bones with large vacuities and thin compact 

 osseous walls and partitions must have been bones of volant vertebrates led to the sup- 

 position that certain fossil eggs belonged either to Pterodactyles or Birds, because the 

 bones of the unexcluded embryo showed the hollow or tubular character. Such eggs in 

 a portion of stone from a quarry in the Island of Ascension were submitted under this 

 impression by Lyell, in 1834, to my examination. The characteristic scapula and 

 coracoid of a chelonian embryo were detected in the petrified contents of the fossil egg. 

 To the objection, based on the hollowness of those limb-bones, against the reference of 

 those bones to the reptilian genus, I showed, by dissection of a newly hatched Chelone 

 preserved in spirits in the Hunterian Museum, that the cavity of such bones was filled 

 with chondrine, not with air, and I explained to my friend that the thin outer shell of 

 bone was a transitory embryonal character, and that the femora, humeri, and other bones 

 became massive and solid in the adult turtle.* Now, the earlier chondrosal stage in the 

 existing genus was not overpassed but retained as the normal adult osteal character of 

 the extinct huge and heavy reptiles of the genus Chondrosfeosaurus. 



It is a relief to banish the marvellous and awful vision of flying Dragons with 

 vertebrae of the size of those of Chondr. giffcis and Chondr. mat/nus ! 



Order. DINOSAUR I A (?). 



Genus — Cardiodon. 

 Species — Cardiodon ruyulosus. 



In the Wealden and Upper Oolitic, as in other mesozoic formations, the evidences 

 studied in the process of restoring the Reptiles of those periods come to hand, for the 

 most part, fragmentarily. Bones without skull, jaws, or teeth may indicate genera 

 before unknown, such as Omosaurus and Chondrosfeosaurus ; or scattered teeth unasso- 

 ciated therewith may suggest reptiles as huge but be generically distinct from the known 



* See note in Lyell's 'Principles of Geology,' vol. ii, p. 292, ed. 1835. 



