642 MICROSCOPIC GEOLOGY. 



dental structure) to which these teeth belonged. They had been 

 referred, from external characters merely, to the order of Saurian 

 Reptiles ; but these characters were by no means conclusive ; and 

 as the nearest approaches to their peculiar internal structure are 

 presented by Fish-Lizards and Lizard-like Fish, it might be rea- 

 sonably expected that the Labyrinthodon would combine with 

 its reptilian characters an affinity to fish. This has been clearly 

 proved to be the case, by the subsequent discovery of parts of its 

 skeleton in which such characters are very obvious ; and by a 

 very beautiful chain of reasoning, Prof. Owen succeeded in 

 establishing a strong probability, that the Labyrinthodon was a 

 gigantic Frog-like animal five or six feet long, with some pecu- 

 liar affinities to Fishes, and a certain mixture also of Crocodilian 

 characters ; and that it made the well-known foot-prints which 

 have been brought to light, after an entombment whose duration 

 can scarcely be conceived (much less estimated), in the Stourton 

 quarries of Cheshire. 



453. The more recent researches of Prof. Quekett on the 

 minute structure of Bone, 1 promise to be scarcely less fruitful in 

 valuable results. From the average size and form of the " lacunse," 

 their disposition in regard to each other and to the Haversian 

 canals, and the number and course of the canaliculi, he feels 

 assured that the nature of even a minute fragment of bone may 

 be determined with a considerable approach to certainty; and 

 the following examples, among many which might be cited, ap- 

 pear to justify such assurance. Dr. Falconer, the distinguished 

 investigator of the fossil remains of the Himalayan region, and 

 the discoverer of the gigantic fossil Tortoise of the Sivalik Hills, 

 having met with certain small bones about which he was doubt- 

 ful, placed them in the hands of Prof. Quekett for minute exami- 

 nation; and was informed, on microscopic evidence, that they 

 might certainly be pronounced Reptilian, and probably belonged 

 to an animal of the tortoise tribe ; and this determination was 

 fully borne out by other evidence, which led Dr. Falconer to con- 

 clude that they were toe bones of his great tortoise. Some frag- 

 ments of bone were found, some years since, in a chalk-pit; 

 which were considered by Prof. Owen to have formed part of the 

 wing-bones of a long-winged sea-bird allied to the Albatross. 

 This determination, founded solely on considerations derived 

 from the very imperfectly preserved external forms of these frag- 

 ments, was called in question by some other palaeontologists; 

 who thought it more probable that these bones belonged to a 

 large species of the extinct genus Pterodactylus, a flying-lizard, 

 whose wing was extended upon a single immensely prolonged 

 digit. No species of Pterodactyle, however, at all comparable 

 to this in dimensions, was at that time known ; and the characters 



1 See his Memoir on the " Comparative Structure of Bone," in the " Transac. of the 

 Microsc. Societ." Ser. 1, vol. ii; and the "Catalogue of the Histological Museum of the 

 Roy. Coll. of Surgeons," vol. ii. 



