Marine Reptiles of the Oxford Clay. 221 



the centre, is the exact inverse of what is found in full-grown 

 animals. One may wonder whether the bad preservation of 

 Pliosaurian dorsal vertebrae from the Oxford Clay may not be due 

 in a large measure to the retention through life of the spongy 

 texture so noticeable in the bones of the young animal. That some 

 peculiarity pertained to this genus seems to follow from the fact that, 

 though distortion from pressure is not uncommon in other classes of 

 Reptilia from this deposit, when it does occur it is not as a rule 

 confined to the dorsal region, whereas in the Pliosaurs the dorsal 

 vertebrse are practically never found in any other condition. 



Dr. Andrews had already published an anticipatory account of the 

 various species which he has distinguished among the large series of 

 Teleosaurian Crocodilia, but in this, the final presentation of the 

 results of his researches, he not only includes a new species in 

 Steneosaums hulkei, but finds himself compelled to refer to an 

 entirely new genus, Mycterosuchiis, the specimens formerly described 

 as Steneosaums nasutus, possessing as it does marked differences in. 

 the structure of some of the vertebrae, the form of the skull and the 

 humerus, and the relative size of the fore and hind limbs. In 

 this connexion it is now shown that in the Steneosaurs, at least, the 

 general characteristics of particular bones in any given species are 

 present throughout the whole skeleton ; thus St. Leedsi, with its slim 

 and slender skull, is associated with sharper teeth, longer and more 

 slender vertebrae, with lighter neural spines. It should now be 

 possible to refer almost any isolated bone to its proper species. It is 

 interesting to note that, though the author can find among the 

 Peterborough Steneosaurs no species exactly comparable with those 

 from the same strata in Northern France, he fully admits in his 

 account of St. hulkei (of which an illustration would have been 

 welcome) the possibility that what are regarded in this Catalogue as 

 specific features may be in part nothing more than age -characters. 

 This statement is important, and is only here rendered possible 

 by the extensive series of skulls, all derived from the same area. 

 On the other hand, it has to be remembered that the variant form 

 of coracoid, as shown in figs. 69 and 70, is found in fully developed 

 representatives of one and the same species. 



The genus Metriorhjnchis vies successfully with Ophthahnosaunis 

 in its frequency in the Peterborough deposits, and is represented in 

 this Catalogue by an unusually fine series of skulls, among which 

 Dr. Andrews recognizes no less than seven species. This is the first 

 time that any comprehensive account of this genus, as found in 

 England, has been published, and the author is to be congratulated 

 on the moderation which he has displayed, amid such a wealth of 

 material to choose from, in creating new species. Here, again, 

 it is probable that age-characters may be responsible for many 

 of the variations which would undoubtedly have aroused some 

 palaeontologists to indulge in a perfect orgy of terminological 

 invention. AVith the distinctions drawn in this Catalogue there can 

 be no complaint on that score. In this genus we come more into touch 

 with the I^ormandy crocodiles, no less than three species named by 

 French scientists being identified in England also. Three species, 



