72                                                                                                     [May, ________

May 23d

Vice-President Bridges in the Chair.

Letters were read --

     From Dr. Wm. Wirtenwerber, dated Prague, 30th. Oct., 1853, transmitting several of his works, acknowledged this evening.

     From Dr. W. D. Hartmann, dated West Chester, Pennsylvania, May 16, 1854, acknowledging the receipt of his notice of election as a Correspondent.

     Dr. LeConte presented a paper by Mr. C. Girard, and intended for publication, entitled "A list of North American Bufonides, with diagnoses of new species." Referred to Dr. Hallowell, Dr. J. Leidy, and Mr. Hanson.

     Dr. Leidy called the attention of the members to specimens of four vertebræ of a huge extinct saurian, from near Greenville, Clark Co., Arkansas. They had been kindly loaned by Mr. W. F. Roberts, an agent of the Arkansas Mining Company, who had discovered them with numerous others. Dr. L. stated, that in his late visit to St. Louis, Mr. Albert Koch, the industrious collector of fossil remains, had exhibited to him a collection of bones from the same State, and apparently of the same animal, which he was on thc eve of sending to Berlin.

     The specimens on the table are remarkable for the robust transverse processes, which project laterally from the lower part of the body, and terminate in a large facet for the articulation of a rib. The bodies are cylindroid, and are terminated by slightly concave or nearly flat articular surfaces. The sides of the body are moderately concave, and have an acute margin at the articular surfaces. On each side of a median prominence of the under side of the body a large vascular foramen exists.

     These vertebræ resemble those of the Cimoliasaurus magnus, from the green sand of New Jersey, described previously in the Proceedings of the Academy,* but in that the large transverse process is cylindrical, while it is compressed cylindroid in the Arkansas saurian, and probably this latter belongs to a distinct genus, for which the name Brimosaurus grandis is proposed. The bones are embedded in a hard limestone with mollusca, and they probably belong to the cretaceous or to the Eocene period. One of the most perfect of the vertebræ presents the following measurements:

               Length of the body.                            3 3/4 inches.

               Depth of articular surfaces.               5            "

               Breadth of    "            "        .               6            "

               Length of the spinal arch.                  3            "

References of Plate II.

Fig. 1-3 Brimosaurus grandis.

Fig. 4-6 Cimoliasaurus magnus.