﻿KIMMERIDGE CLAY. 71 



" b. Saurier mit Gliedmassen ahnlich denen der schweren Landsaiigetliiere. 1. 

 Megalosaurus, BucMand. 2. Iguanodon, Mantell" 



"c. Saurier mit flossartigen Gliedmassen. 1. Ichthyosaurus, Konig. 2. Plesiosaurns, 

 ■Conyheare. 3. Mosasaurus, Conybeare. Streptospondylus, H. v. M.'' 



"d. Saurier mit Flughaut. Pterodactylus, Cuvier" (Op. cit., p. 201). 



In the characters of his subordinate group b, Von Meyer (lb., p. 210) condenses the 

 descriptions and accepts the determinations, clavicle included, of Buckland and Mantell. 

 There is no sign of his having examined any of the fossils on which these descriptions 

 and determinations were based. He is struck with a resemblance of the metapodial 

 bones of Megalosaurus in Buckland's plates with those of a hippopotamus ; and with the 

 size of one of these bones, " zweimal so breit als im Elephanten" of the Iguanodon ; and 

 may have deemed their feet, in like manner, to have been tetradactyle or pentadactyle. 

 Such supposed character seems to have suggested to Von Meyer the name Pachypoda, 

 which he subsequently applied to them, the proportions of the entire foot which would 

 support such term being to him unknown. 



The feet of Dinosaurs are, in fact, characterised by their narrowness or slenderness 

 rather than by their breadth or thickness. The functional toes (hind feet), are, in the 

 typical species of Von Meyer's Pachypoda reduced to three, 1 and do not exceed four [Sceli- 

 dosaurus, e. g.) in any veritable member of the order. But had Von Meyer known the 

 structure of the Dinosaurian foot, and it had been such as to have been truly defined by 

 his 'family term,' this term must have given way to the "Pachypoda" proposed and 

 accepted in 1821 for a similar group of Mollusca ; as the same term, proposed for a family 

 of Coleoptera, in 1840, had, in like obedience to taxonomic rules, sunk to the condition of 

 a synonym under the law of priority, even when not affected by inapplicability of the name 

 to its objects. 2 



Every specimen accessible in 1840, of Megalosaur, Iguanodon, Hylgeosaur, having been 

 examined and compared by me and the structure of the sacrum elucidated by observations 

 on its development in birds, 3 vertebral characters, with dental ones, were substituted for 

 those of the Family above cited from the ' Isis' and ' Palseologica,' in the definition of the 

 Order Dinosauria, quoted by Professor Huxley in his paper on this group. 4 Of this defi- 

 nition the Professor asserts that "every character which is here added to von Meyer's 

 diagnosis and description of his Pachypoda has failed to stand the test of critical inves- 

 tigation.'' 5 This statement is not accompanied with any evidence in its support, but is 

 suggestive that I had dealt unjustly with von Meyer in proposing the name and substi- 



1 E.g. Ily Iceosaurus (' Monogr. Wealden Reptilia,' Pal. vol. for 1856, p. 18, pi. xi) ; Iguanodon 

 ('Monogr. AVealden Reptilia; Pal. vol. for 1856, p. 1, pi. i). 



2 Pachypus was given to a genus of Coleoptera in 1821 ; this, in like manner, reduced the Pachypus 

 applied to a genus of mammals in 1839 to a synonym. 



3 'Report on British Fossil Reptiles,' p. 106, 1841. 



4 ' Quarterly Journal of the Geological Society,' vol. xxvi, p. 32, 1870. 



5 lb., p. 33. 



