238 BRITISH FOSSIL REPTILES. 



With the exception of one restricted family of Ruminants, every Mammal, the 

 blood-discs of which have been submitted to examination, has been found to possess 

 those particles of a circular form : in the Camelidee they are elliptical, as in birds and 

 reptiles. The bone-cells have already shown a greater range of variety in the 

 vertebrate series than the blood-discs. Is it, then, a too scrupulous reticence, to 

 require the evidence of microscopic structure of a bone to be corroborated by other 

 testimony of a plainer kind, before hastening to an absolute determination of its nature, 

 as has been done with regard to the Wealden bone, figured in the ' Geological Trans- 

 actions," vol. V, pi. xiii, fig. 6 ?* 



As a matter of fact, the existence of Pterodactylian remains in Chalk was not sur- 

 mised through any observation of the microscopic structure of bones that are liable to 

 be mistaken from their more obvious characters for those of birds, but by the dis- 

 covery of the characteristic portions of the Pterodactyle, defined by Mr. Bowerbank, 

 as follows, in his original communication of their discovery to the ' Geological Society 

 of London,' May 14th, 1845. 



" I have recently obtained from the Upper Chalkf of Kent, some remains of a 

 large species of Pterodactylus. The bones consist of — 



1. "The fore part of the head, as far as about the middle of the cavifas narhnn, 

 with a corresponding portion of the under jaws, — many of the teeth remaining in their 

 sockets, (see PI. 1, fig. 1.) 



2. " A fragment of the bone of the same animal, apparently a part of the coracoid, 



(fig. 2.) 



3. " A portion of what appears to be one of the bones of the auricular digit, from 

 a Chalk-pit at Hailing, (fig. 3.) 



4. " A portion of a similar bone, from the same locality as No. 1, (fig. 4.) 



5. " The head of a long bone, probably the tibia, belonging to the same animal as 

 the head, No. 1, (fig. 5.) 



6. " A more perfect bone of the same description, not from the same animal, but 

 found at Hailing," (fig. 6.) 



In a subsequent communication, dated December 1845, Mr. Bowerbank states, with 

 regard to the specimens, Nos. 5 and 6, which he supposed to be parts of a tibia, that 

 " on a more careful comparison with the figures of Fterodactylm by Goldfuss, I am 

 inclined to believe they are more likely to be portions of the ulna." 



* I would request the reader who may be desirous to exercise an independent judgement ou such 

 facts as have been published on this point, to compare, for example, some of the cells figured by 

 Mr. Bowerbank, in PI. i, fig. !), of the ' Quarterly Journal of the Geological Society,' vol. iv, as being those 

 of the bone of a bird, with some of the wider cells, fig. 1, of the same plate, as being those of the 

 bone of a Pterodactyle ; and contrast the want of a parallelism in the cells of the Wealden bone, fig. 9, 

 with the parallelism of the long axes of the cells in the bone of the Albatross, fig. 3. 

 f See the Note, ante, p. 80. 



