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Show 1888.] ON THE SKELETAL ANATOMY OF THE MESOSUCHIA. 417 1. Contribution to the Skeletal Anatomy of the Mesosuchia based on Fossil Remains from the Clays near Peterborough in the Collection of A. Leeds, Esq. By J. W . HULKE, F.Z.S. [Eeceived July 14, 1888.] (Plates XVIII. & XIX.) The primary divisions of the Order Crocodilia laid down by Cuvier (1), and extended by R. O w e n (2) and by T. Huxley (3), are so true to nature that they have been substantially adopted by all subsequent writers and have proved insusceptible of material modification. However, within these great divisions the classification of the Crocodilia has, as Strauch truly remarks with reference to its extant members, ever constituted one of the more difficult tasks of the systematic herpetologist (4). This he rightly attributes principally to the small amount of material available for an exhaustive study of the entire skeleton of the several Crocodilian species preserved in our Museums, and in some measure to the mutable nature of those parts from which the systematic herpetologist has mainly taken the distinctive characters he employs, viz.-the skull, in which the proportions of the proper cranial and the facial region notably alter with the age of the individual in all species; and the integument, the scutes of which exhibit, within limits, differences as regards their shape and their arrangement in the same species. Even now, after an interval of more than twenty years since the publication of Strauch's admirable synopsis (5), no public osteological collection in this metropolis, so far as I can ascertain, possesses a series illustrating the changes of form which the Crocodilian skeleton undergoes in its growth from the young to the mature individual in any one species. Indeed as regards o n e- Gavialis, and this not the least important, I find that neither the British Museum nor that of the Royal College of Surgeons contains a single entire skeleton. The latter, however, possesses a few detached bones of this genus (crania are well represented in both collections). Exact and comprehensive anatomical knowledge not limited to external features, but extended to the whole skeleton and to the soft parts, must form the only safe basis of any enduring classification. As regards the extinct members of the Order, the difficulties are for very obvious reasons greatly increased. Highly instructive as are the magnificent skeletons bedded in slabs of rock that adorn our galleries, these often fail to afford information respecting forms and structural details which yet m ay be of first-rate importance. Obviously many such details can only be apprehended by the study of detached bones that can be separately handled, and be viewed in turn from every side. It is the facility for such study that gives a high value to a large collection of Crocodilian remains from pits opened in |
