vi MAEINE EEPTILES OF THE OXFOED CLAY. 



as easily as if tliey had been obtained by the maceration of a fresh carcass. A notable 

 instance of this is the fine skeleton (E. 2860) of Cryptocleidus oxoniensis, which is 

 figured on the Frontispiece and forms the basis of the restoration given in text-figure 94 

 on page 188. In this case, as in many others, the bones, whicli all belong to a single 

 individual, are uncrushed and undistorted. Often, however, the skeletons have been 

 subjected to great pressure, and have thus been extensively fractured and deformed. 

 Unfortunately the skulls are especially liable to injury, and therefore any specimens 

 approaching completeness are very rare. Occasionally the whole skeleton or portions 

 of it are embedded in an intensely hard pyritous clay, and when this is the case all 

 attempts at clearing away the matrix are usually hopeless. Another cause of the 

 imperfection of many of the skeletons seems to have been the dismemberment of the 

 carcasses by carnivorous reptiles, probably some of the Crocodiles and Pliosaurs whose 

 remains are also common in the Oxford Clay. Bones are often found scored across 

 by deep grooves, obviously cut by sharply pointed teeth. Moreover, the curious 

 manner in which whole sections of the skeleton, as, for example, a limb, are sometimes 

 wanting in otherwise nearly complete specimens, or, on the other hand, the occurrence 

 of isolated paddles and other parts of the skeleton, seems to show that the dismember- 

 ment occurred while the bones were still united by the soft tissues. A notable instance 

 of this incompleteness is seen in the case of the portions of the skeleton of the giant 

 Dinosaur, Cctiosaurus leedsi, described and figured by Dr. A. S. Woodward (Proc. Zool. 

 Soc. 1905). In this specimen, the skull, the whole of the vertebral column in front of 

 the sacral region, the left fore limb and the right hind limb, as well as the iscliia and 

 pubes, are wanting, while the left hind limb is almost complete, even to the phalanges, 

 also the right fore limb except the manus ; the vertebral column of the tail, again, 

 is represented by two series of successive and complete vertebras, an anterior series of 

 about 27, and a posterior one of 10, while the intervening portion is entirely absent. 

 Although careful search and extensive excavations have been made, none of the missing 

 parts have been found, and such absence of whole sections of the body seems to be 

 best explained by supposing the carcass to have been dismembered while the bones 

 were still united. 



The horizon at which these reptilian bones occur is that characterised by the 

 presence of the *' Ornatus'' group of Ammonites, one of the species most 

 commonly found in actual association with the bones being Cosmoceras gulielmii. 



