On Macrurosaurus semnus (Seeley), a Long tailed Animal with Procœlous Vertebræ from the Cambridge Upper Greensand, preserved in the Woodwardian Museum of the University of Cambridge

Abstract

A bout twelve years ago the Woodwardian Museum acquired from Mr. W. Farren a series of some 25 associated and successive caudal vertebræ, found at one of the deeper phosphatite washings on Coldham Common, Barnwell. At the same date, the Rev. W. Stokes Shaw, M.A., Caius College, obtained from a similar working at Barton, a locality a few miles westward, another associated series of 15 smaller vertebræ showing identical characters, and of such size as to exactly join on to the first series and complete the tail. These latter vertebræ, not improbably part of the same individual, being presented to the Museum, I arranged both sets in a continuous series. Very few appear to be missing in any part of the sequence, though the extremity of the tail is probably not preserved, and there are no means of estimating how many vertebræ may have intervened between the last of the sacral region and the earliest caudal which is preserved. The tail probably included 50 vertebræ, and may have reached a length of 15 feet, which would have amounted to one half the length of the animal if the proportions of modem crocodiles obtained. A few isolated vertebræ have also been collected; but no distinctive portions of the skeleton have come under my notice. The affinities of the animal are at present somewhat obscure; for the only available data from which a determination could be made are the following facts:- The articulation of the earlier vertebræ is procœlous; this character gradually changes