72 



FOSSIL REPTILIA OF THE 



Buckland's Memoir, and suggested that its subject might belong to the same section or 

 genus.^ The subsequent discovery of the skull and dentition has, however, shown that 

 another generic section of Fterosauria, or at least one species thereof, had a similar long 

 and stiff tail. The modification involving that quality does not, however, extend 

 throughout ; the anterior caudal vertebrae retain the more normal character, and the 

 appendage would be most moveable at its base. No doubt a small degree of yielding at 

 the many persistent vertebral joints — for complete anchylosis has not been observed — 

 would allow a slight curvature to the extent to which the tail is represented as yielding 

 to a lateral force in the restored figure (PI. XX, fig. 2). The number of the caudal 

 vertebrtE in Dimorphodon macroiryx was at least thirty ; the termination of the specimen 

 figured in PI. XIX, fig. 4, does not indicate a loss there of as many centrums as would 

 bring the number up to thirty-eight, which are assigned by Von Meyer to his Rhampho- 

 rhynchus Genmingi. 



As we cannot, therefore, with Soemmerring, insist on the shortness of the tail in some 

 Pterosauria as proof that they were Birds, so neither can w^e conclude from the length of 

 the tail in other Pterosauria that they were Reptiles. The legitimate taxonomic deduction 

 from such caudal modifications is, that they are not of sufficient importance for determi- 

 nation of a class, and that they do not exclusively characterise the genus. They 

 indicate adaptations in an extreme and variable part or appendage of the body to special 

 powers or ways of movement, or sustentation, in air of the present group of volant animals. 



So, likewise, it cannot be, as it has been, inferred from the length of tail in Arc]i<sopteryx, 

 that it was a Reptile." What Ave learn from that Avian fossil is akin to what we 

 have learnt from Pterosaurian remains, viz., that the tail is a seat of extreme modification, in 

 respect of length and number of joints, within the limits of the feathered class. Mamma- 

 logists, with a like drift, could add instructive evidence of corresponding caudal variability 

 within the limits of the order, as in the volant Cheiroptera, and even within the bounds of 

 the family {Bradi/pus and Megatherium, e.g.). 



The value of the discovery of Archceopteryx, in relation to Pterosauria, is enhanced by 

 the peculiar nature of the matrix, conservative of cutaneous as well as of osseous 

 characters ; showing casts of down and feathers,^ impressions of the fine foldings or 

 wrinkles of thin expansions of naked skin, as well as delicate tendons surrounding, 

 working, strengthening, and stiffening the caudal framework. 



With these parts the fine lithographic lime-marl should have preserved the plumose 

 appendages of the long tail oi Ithainphorhynchus,\i that flying Reptile had possessed such ; 

 and, along with caudal plumes and vertebrae, should have been preserved the bone-tendons 

 of the tail, if Archceopteryx had possessed that structure. 



It is probable, from the constancy with which caudal vertebra3 of long-tailed 



1 In 'Leonhard und Bronn's Neues Jalirbuch fiir Miiieralogie,' &c., Jalirgang, 1857, p. 536. 



2 E.g., as the Gryphosaurus of Andreas Wagner. 



^ .\ few of tlie delicate, downy body-feathers of ArchcEopterijx are clearly indicated near one side of the 

 trunk in the slab with most of the bones of the specimen of Archaopteryx in the British Museum. 



