dinosaurian reptile from the Portland Limestone of Beagle Pit, Hart- well near Aylesbury, which have been described by the present writer [1] under the name of Pelorosaurus humerocristatus. The genus Pelorosaurus, it may be observed, was founded on the evidence of a huge bone (humerus) of the fore-limb from the Wealden of Sussex. And since American specimens have shown that reptiles allied to this genus possessed teeth of the type of those from Hartwell it is a fair infer- ence that the latter belong to Pelorosaurus, although not to the same species as the one indicated by the Wealden humerus. Three other teeth from the same locality and formation belong to another and very different type of dinosaurian reptile, namely the carnivorous Megalosaurus, whose remains were first discovered in the middle Jurassic strata of Oxfordshire. These teeth have been described by Dr. Smith Woodward [2] without being specifically determined. A long-necked plesiosaurian reptile, Cimoliosaurus portlandicus, has left its remains in the Portland formation of Quainton ; the Buckinghamshire specimens having been originally described under the name of Plesiosaurus carinatus. Ichthyo- saurian remains are also reported, although not described, from Hartwell.
The Kimeridge Clay of the county has apparently hitherto yielded very few vertebrate remains. A fish-spine from this formation at Hartwell has however been assigned to the common Jurassic type known as Asteracanthus ornatissimus, which may belong either to a shark or to a chimaera-like fish. From the same locality have been obtained remains of the great short-necked and large-headed plesiosaurian known as Pliosaurus macromerus, the teeth of which are characterized by their triangular crowns.
The British Museum possesses a limb bone of a plesiosaurian, or long-necked marine saurian, from the Kimeridge Clay of Newport Pagnell, which is assigned to Colymbosaurus trochanterius, a species widely distributed in the formation in question. Among the fish-lizards the species Ichthyosaurus thyreospondylus is represented in the county by a bone obtained from the Oxford or Kimeridge Clay near Buckingham.
From the Great Oolite of Buckingham and Stony Stratford Pro- fessor J. Phillips records (Geology of Oxford) remains assigned to the great dinosaurian reptile commonly known as Cetiosaurus oxoniensis, but of which the proper title is probably Cardiodon rugulosus.
26
