A fragment of the lower jaw of a large Ornithocheirus has been obtained from an outlier of the Upper Greensand at Rocken End in the Isle of Wight. It appears to indicate a distinct species. It is 2-1/2 inches long, and shows three large teeth still preserved in their sockets. The extreme width outside the third pair of sockets is nearly 2 inches. The sides, which are slightly concave from above downward, converge so as to give the broken end a triangular outline. In front is a small sub-triangular area, deeply scored with vascular markings; below this the outline slopes obliquely backward, and the two sides there round convexly into each other. The first socket is 7/16ths of an inch long, the tooth coarsely striated, and like the others elliptical; the interspace between the first and the second teeth is 5/16ths of an inch. The second tooth, probably immature, is an inch in length, smooth, and like the third traversed in front and behind by a slight lateral ridge; at the base it measures 5/16ths of an inch from front to back. The third tooth is rather less than 5/8ths of an inch from front to back. The interspace between the first and second _sockets_, which the teeth do not entirely fill, is more than 1/4 of an inch. The posterior margin of each socket is elevated into a sort of collar. APPENDIX. _Enumeration of some of the principal writings on the Ornithosauria (selected chiefly from Von Meyer's Reptilien aus dem Lithographischen Schiefer), with references to the shelves in the Cambridge University Library, where the books may be consulted._ Agassiz (Louis).--Memoires Soc. Nat. Neuchâtel, Vol. 1, p. 19, _paragraph notice in a memoir_, "Résumé des travaux de la section d'histoire naturelle, et de celle des sciences medicales pendant l'année, 1833" B. 3. 66. A briefer notice in a paper, "A Period in the History of our Planet," in Edinburgh New Phil. Journal, 1843, Vol. 35, p. 9, quoted by Von Meyer XXVIII. 36. 65. de Blainville (D.).--Osteographie; Palæotherium, p. 9 (Vol. 2), quoted by v. Meyer AF. 5. 9. Bonaparte (C. L.).--Nuovi Annali delle Scienze Naturali Bologna[1], Vol. 1, 1838, p. 391; Vol. 4, 1840, 24 Sept. p. 91. Blumenbach.--Manuel d'Histoire naturelle, éd. 1803, Vol. 2, p. 408 B. 12. 20. (Vergleichende Anatomie, 1805, p. 75), § 44, Translation, 1807 Tt. 18. 51. Handbuch der Naturgeschichte, 1825, p. 620 Yy. 39. 6. Burmeister.--Gesellsch. zu Halle, Vol. 3, Part 2, 1855; Viertel-jahrsbericht, 28 April, p. 11 XXVI. 50. 2. Collini.--Acta Acad. Theod. Palat. 1784, Vol. 5, p. 58, pl. 1. 17. 5. 34.