ME. J. BACKHOirSE OX A MAXDIBLE OF MACHiERODUS. 309 



24. On a Mandible of Mach^rodtjs from the Forest-bed. By 

 James Backhouse, Esq., F.G.S. With an Appendix by Rr 

 Ltdekker, Esq., B.A., F.G.S. (Read April 7, 1886.) 



[Plate X.] 



Abotjt two months ago I obtained from the Forest-bed of Kessing- 

 land, Suffolk, a specimen which I take to be the right mandibular 

 ramus of a species of Machcerodus (Plate X.). As I believe that no 

 example of the lower jaw of any species of this genus has been met 

 with in this country, I venture to send the following description of it. 



Length from posterior margin of condyle to upper edge of sym- 

 physis at insertion of second incisor 204 mm. 



Vertical depth below premolar at shallowest part of ramus 38*25 

 mm. 



Depth at middle of diastema 51 mm. 



Depth at lowest point of symphysis 63*75. Originally the depth 

 at this point has apparently been 70, if not 75 mm. 



The diastema is large (41 mm.) and, like the portion of the ramus 

 immediately beneath it, curved inwards ; it presents a fossa of 6 or 7 

 mm., from the direct line between the canine and cheek-teeth, for 

 the accommodation of the upper canine. The anterior foramen is 

 large, and in a line parallel to the adjo,ining base of the ramus. 

 The condyle is imperfect, the length of the remaining portion being 

 38-2 mm., and the vertical thickness 19-1 mm. The coronoid pro- 

 cess has lost its upper third, the remaining portion being 25 mm. 

 in height and 38 mm. in width at the base. 



In regard to the teeth, the sectorial has an antero-posterior 

 diameter of 32 mm. ; it is much worn diagonally by the action of 

 the corresponding upper tooth, and anteriorly overlaps the premolar. 

 The premolar has an antero-posterior diameter of 22*25 mm. ; it is 

 split vertically, while the apex of its anterior cusp and the outer 

 edge have been worn away. The total length of the upper surface 

 of the two teeth is 51 mm. The canine is likewise partially worn 

 away and has lost its upper portion, the length of the remaining 

 portion being 25 mm., and the breadth 15 mm. The first incisor 

 has well-marked cusps, but wants its upper portion ; its width is 

 11 mm. The second has a width of 7 mm., and a depth (back to 

 front) of 11 mm. 



Appendix by R. Ltdekker, Esq. 



With the consent of Mr. Backhouse I append a short note, in the 

 hope that it may more fully elucidate the affinity of his interesting 

 specimen, which undoubtedly belongs to Machcerodus. 1 may ob- 

 serve, first of all, that the Macha^rodus of Pikermi* and Eppelsheim f 



* M. leoninus, Wagner. t M. (F.) aphanistus, Kaup. 



