24 



vol. vi. pi. 39, was a most improbable one to have sustained a power- 

 ful wing of any bird ! * Let me not be supposed, however, to be 

 concerned in excusing my own mistake ; I am only reducing the 

 unamiable exaggeration of it. Above all things, in our attempt to 

 gain a prospect of an miknown world by the difficult ascent of the 

 fragmentary ruins of a former temple of Hfe, we ought to note the 

 successful efforts, as well as the occasional deviations from the right 

 track, with an equal glance, and record them with a strict regard to 

 truth. The existence of a species of Albatros, or of any other actual 

 genus of bird during the period of the Middle Chalk, would be truly 

 a wonder of Geology ; not so the existence of a bird of the longipen- 

 nate family. 



I still think it for the interest of science, in the present limited 

 extent of induction from microscopic observation, to offer a warning 

 against a too hasty and implicit confidence in the forms and propor- 

 tions of the Purkingean or radiated corpuscles of bone, as demon- 

 strative of such minor groups of a class as that of the genus Ptero- 

 dactylus. Such a statement as that " these cells in Birds have a 

 breadth in proportion to their length of from one to four or five ; 

 while in Reptiles the length exceeds the breadth ten or twelve times," 

 only betrays the limited experience of the assertor. In the dermal 

 plates of the Tortoise, e. g., the average breadth of the bone-cell to 

 its length is as one to six, and single ones might be selected of greater 

 breadth. 



With the exception of one restricted family of Ruminants, every 

 Mammal, the blood-discs of which have been submitted to examina- 

 tion, 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 corrobo- 

 rated by other testimony of a plainer kind, before hastening to an 

 absolute determination of its nature, as has been done vnth regard to 

 the Wealden bone, figured in the Geol. Trans., 2nd Series, vol. v. 

 pi. 13. fig. Gf ? As a matter of fact, the existence of Pterodactylian 

 remains in the chalk was not surmised through any observation of the 

 microscopic structure of bones that are liable to be mistaken for those 

 of birds, but was first plainly proved by the characteristic portions of 

 the Pterodactyle defined by Mr. Bowerbank, as follows, in his original 

 communication of this discover)' to the Geological Society of London, 

 May 14, 1845 :— 



" I have recently obtained from the Upper Chalk :J; of Kent some 



* Mantell, 'Wonders,' &c. ed. 1848, vol. i. p. 441. 



t Compare, for example, two of the longest of the cells figured by Mr. Bower- 

 bank in pi. 1. fig. 9, ' Quarterly Journal of the Geological Society,' vol. iv. as those of 

 a bird, with two of the widest of the cells figured in fig. 1 of the same plate as those 

 of the Pterodactyle ; and contrast the want of paralleUsni in the bone-cells of the 

 M''ealden bone, fig. 9, with the parallelism of the long axes of the cells in that of 

 the Albatros, fig. 3. 



X Mr. Touhnin Smith, in an able paper " On the Formation of the Fhnts of the 



