Sub-order 3. Opisthocoezlia

The sub-order of the Opisthocoelian Crocodiles, including those forms in which the anterior trunk vertebrae are concave behind, is one which can be only provisionally retained. Professor Owen includes in this section the two genera Streptospondylus and Cetio-saurus; but the latter is referable to the Deinosauria, and will be treated of when that order is considered. The genus Streptospondylus has been founded on vertebrae obtained from the Oolitic and Wealden formations; but there are doubts as to the true position of the reptile to which these belonged.