HARDWICKE'S SCIENCE-GOSSIP. 



223 



The great similarity between some of the bones of 

 the Tterosauria, and the corresponding parts of the 

 skeleton in certain orders of birds, constitutes perhaps 

 the most important obstacle to the correct determina- 

 tion of the Avian fauna of the Mesozoic age. More 

 than once, specimens have been described by the 

 highest authorities as indicating the existence of birds 

 at particular periods ; while some time afterwards the 

 same palaeontologists have altered their opinion, in 

 consequence of longer consideration and greater 

 experience, and declared the puzzling fossils to be 

 truly pterosaurian.* In fact, the Pterosauria seem to 

 graduate so imperceptibly into the Aves, that it is 

 hard to ascertain in many cases whether a skeletal 

 fragment belongs to the former or the latter class, 

 and, as palaeontological research continues, many 

 intermediate forms will probably be defined, to 

 which a large proportion of the problematical bones 

 may eventually be referred. 



So long ago as 1S35, Dr. Mantell announced the 

 discovery, in the Wealden Strata of Tilgate Forest, 

 of certain fossils which he regarded as belonging to 

 the skeletons of true birds. The remains were very 

 fragmentary, but still, in the opinion both of the dis- 

 coverer, and of Professor Owen, they were considered 

 quite sufficient to warrant the conclusions expressed 

 in the transactions of the Geological Society of London 

 for that year. At a later date, however, after more 

 of the enveloping matrix had been removed from 

 the specimens, Professor Owen studied them more 

 closely, with the result that they were relegated to 

 the Pterodactyles. Since then, no more discoveries 

 of bird-remains in the Weald have been recorded, and, 

 consequently, although the class may have been 

 represented in British regions rat the epoch when 

 that estuarine formation accumulated, no satisfactory 

 evidence of such being the case has hitherto been 

 obtained. 



The next Mesozoic deposit which has been stated 

 to contain traces of birds is the Cambridge (or 

 " Upper") Greensand. In 1858, Mr. Lucas Barrett 

 discovered a few fossil bones, the avian affinities of 

 which were soon recognised, the determination being 

 confirmed by Professor Owen. Subsequently, more 

 specimens were obtained, and the collection of the 

 Woodwardian Museum at Cambridge, comprises a 

 good series of vertebra?, and portions of cranium, 

 femur, tibia, and metatarsus. According to Professor 

 Seeley, who made a careful study of these fragmen- 

 tary fossils, and 'published his final conclusions in 

 1876, there are probably indications of only one 

 genus, but of this there are two well-marked species. 

 Though the remains differ generically from the 

 corresponding parts of the skeleton of any known 

 living bird, the whole series betokens affinities with 

 the existing divers, and in that respect the British 



* For some years a considerable number of the Pterodactyl 

 bones from the Stonesfield slate were looked upon as belonging 

 to birds. 



Greensand specimens somewhat appro ich the in- 

 teresting and peculiar forms discovered in the 

 cretaceous formations of North America. No por- 

 tions of mandibles have yet been discovered in the 

 Cambridge deposit, but taking into consideration 

 all the facts adduced by the fragments of the skeleton 

 already found, it is not in the least improbable that 

 these British cretaceous birds were characterised by 

 the feature of possessing teeth in sockets in the jaw, 

 like the more perfectly known species (of genera 

 Ichthyornis, Hcspcrornis, &c.) in the New World. 

 Some of the bones, and parts of the vertebral 

 column in both the Cambridge Greensand species 

 " shew evidence of remarkable persistence of carti- 

 laginous conditions of the articulations, especially 

 in the region of the dorsal vertebrae" (Seeley). 

 Originally, Pelagornis was the generic name proposed 

 to be applied to these interesting fossils, but, that 

 having been pre-occupied by M. Lartet for a bird 

 (P. mioccenus) discovered in the marine Molasse of 

 Armagnac, it was, in 1876, replaced by the new 

 term, Enaliornis ; the larger species is named E. 

 Barretti, and the smaller, E. Sedgwickii. 



While at the present time palaeontologists are 

 almost universally agreed that the existence of birds 

 at the period of the deposition of the Cambridge 

 Greensand is a well-established fact, such is not the 

 case with regard to the evidence which the chalk has 

 been supposed to afford of the presence in the British 

 area at another period of the same class of creatures. 

 Two imperfect fossil bones were found in 1839, in 

 the chalk of Burham (Kent), which were believed to 

 be of the avian type by Dr. Bowerbank and Professor 

 Owen, and the latter eminent anatomist briefly 

 described the specimens in the Trans. Geol. Soc. 

 Lond. for 1840, indicating their affinities to the longi- 

 pennate natatorial birds — particularly the albatross. 

 Subsequently he proposed to refer the remains to a 

 new genus, j designated Cimoliornis, and from the 

 remarkable resemblances of the species to the 

 albatross, the specific name selected was diomedens. 



Some years afterwards, however, there were dis- 

 covered in the chalk, also at Burham, a few 

 comparatively perfect relics of a huge unknown 

 species of Pterodactyl. These came under the notice 

 of Dr. Bowerbank, and he gave the name of Ptero- 

 dactylus giganteus to the interesting pterosaurian 

 form that they indicated. Somewhat later, this 

 palaeontologist, together with Professor Owen, 

 recognised that Cimoliornis could no longer be 

 looked upon as an extinct bird, and that the 

 imperfect remains upon which the genus had been 

 founded really belonged to the remarkable new 

 species of flying reptile just mentioned. 



The Cambridge Greensand, therefore, is the only 

 British Mesozoic formation which has, so far, yielded 

 satisfactory specimens of the fossil remains of birds. 



(To be continued.) 



