Nearly every writer on Pterodactyles, who has expressed any opinion at all, has formed an estimate of his own of their organization. They have been assigned to almost all possible positions in the vertebrate province, by great anatomists who all had before them very similar materials. An account of these views is given by von Meyer in his monograph of the Pterodactyles of the Lithographic Slate. It will not be necessary to discuss these conclusions here, for the materials from the Lithographic Slate and those from the Cambridge Greensand are so different that no light would be thrown on the organization of the animals by an exposition of any fallacious inferences from German specimens. In England they are classed with Reptilia, chiefly through the influence of the discourse upon them given by Baron Cuvier in his _Ossemens Fossiles_[A]. It therefore may conduce to a clear view of the subject to quote in Cuvier's words the passages in that memoir which have been supposed to establish their position among reptiles. He says,--"Ayant encore porté mon attention sur le petit os cylindrique marqué _g_ (i.e. os quadratum) qui va du crâne à l'articulation des mâchoires, je me crus muni de tout ce qui étoit nécessaire pour classer ostéologiquement notre animal parmi les reptiles." The exact relations of the quadrate bone are not seen in either Cuvier's or Goldfuss' or von Meyer's figures of this Pterodactyle, the P. longirostris; but in von Meyer's figures of P. crassirostris, P. longicollum, and P. Kochi it appears to be a free bone articulated to the squamosal and petrosal region of the skull and with the lower jaw. This is not the case with either Chelonians or Crocodiles, which have the quadrate bone firmly packed in the skull; nor is it paralleled even among those lizards and serpents which have the bone as free; while, on the contrary, it is characteristic of the whole class of birds. The form of the bone is not more Lacertian than Avian, while its direct attachment to the bone of the brain-case finds no parallel among lizards, but is exactly paralleled in all birds. [Footnote A: Tome V. Part a, pp. 358, 383. Edition, 1814.] Cuvier then goes on to say, "Ce n'étoit pas non plus un oiseau, quoiqu'il eût été rapporté aux oiseaux palmipèdes par un grand naturaliste[B]." Which position he supports as follows:-- [Footnote B: Blumenbach.]