In the _lumbar_ region the vertebræ regain their cylindrical form, and become still more elongate; but the cups are comparatively shallow and the heads low; there is no distinct shoulder. The neural canal is small, with low, broad neurapophyses, from which are developed very broad and depressed diapophyses, which project outwards in a horizontal plane. The neural spines are thick, and broad antero-posteriorly, but are so broken that their height cannot be determined. In both dorsal and lumbar region the neurapophyses are deeply notched on their posterior edges, and close to the neuro-central sutures, for the passage of the spinal nerves. The _ilium_ is very high compared with most crocodiles; its vertical diameter is considerably more than half of the antero-posterior diameter. The construction of the bone is very much like that in the modern _Crocodilia_; but the suprailiac border is more regular, and the anterior tuberosity is not so thick or so much everted as in these forms. The acetabulum is small, shallow, directed downwards and outwards, and situated considerably forward of the median line. The iliac surface is smooth, but very irregular, being very deeply concave above the acetabulum, and convex behind it. The sacral surface is rugose, rises above the sacrum, and shows attachments for two sacral vertebræ. Thus the construction of the entire pelvis shows but very little variation from the modern type. _Measurements._ M. Antero-posterior diameter of ilium ·095 Vertical diameter of ilium ·061 Antero-posterior diameter of acetabulum ·029 Length of centrum of third (?) cervical vertebra (from edge of cup to tip of ball) ·032 Height of neural canal, third (?) cervical ·0095 Length of hypapophysis of third cervical ·0085 Length of centrum of a posterior dorsal ·040 Length of diapophysis (about) ·032 Length of centrum of a lumbar ·046 Vertical diameter of a lumbar ·029 Breadth of neurapophysis of a lumbar ·027 Crocodilus heterodon, Cope. _Alligator heterodon_, Proc. American Philosophical Society, 1872, p. 544. Represented by a single tooth from the posterior part of the mandibular series. It agrees very closely with the corresponding tooth of _Alligator mississippiensis_, but presents some differences. The crown is very low, obtuse, and finely striate; it is compressed and shows a cutting-edge. Its longest diameter is fore-and-aft; both this and the transverse diameter are proportionately greater than in the modern species. The constriction of the neck is very decided; the fang is large, and especially thick. _Measurements._