the Recent and Fossil Beaver. 53 



fen-deposit, the breadth of the olecromal part of the articular 

 trochlea of the humerus is 0*010 = 5 lines ; in Trogontherium it is 

 023 ^10^ lines. The breadth of the fore part of the trochlea in 

 Castor is 0-019 = 9 lines ; in Trogontherium it is 0*024 = 11^ lines ; 

 the antero-posterior diameter of the radial tuberosity of the humeral 

 trochlea in Castor is 0*008 = 4 lines ; in Trogontherium it is 0*020 = 

 9 lines. 



The femur, PI. IIT. Figs. 1 and 2, was obtained by theEev. Jolin 

 Gunn, M.A., F.G.S., from the Forest-bed, at Mundesley. A faint 

 trace of the distal epiphysial line indicates it to have belonged to a 

 young, but nearly, if not quite, full-grown animal. The processes, 

 ridges, rough pits, etc., indicative of muscular insertions and actions, 

 are well-marked. 



Among the characters of the femur in the order Bodentia may be 

 noted, a slender femoral neck, high trochanter major with deep 

 trochanterian fossa, well-marked trochanter minor, a third trochan- 

 terian process or ridge, distinctive of the rotular articular surface 

 from that of the condyles. These characters do not concur in every 

 rodent femur, but are found in most. They are present in the fossil 

 in question ; the third trochanter being represented by a long ridge, 

 Fig. 1, e, d, but the present bone has not the ordinary cyclindrical 

 shaft of the rodent femur, being rather flattened from before back- 

 ward, and expanding transversely at the distal half. 



The above characters sway me to the conclusion that the specimen 

 in question is the femur of a large rodent quadruped ; the shape of 

 the shaft, and other characters presently to be noticed incline me to 

 refer such rodent to the beaver-family (Castor idee), Hitherto, no 

 evidence of a large rodent animal has turned up in any locality 

 of the Norfolk littoral Forest-bed, save that to which the teeth and 

 portions of jaws above described or referred to, belong, viz., the 

 Trogontherium Cuvieri. I, therefore, deem- it highly probable that 

 we have in Mr. Gunn's unique specimen (now, by the liberality of 

 that acute and perseveruig investigator of the geology and fossils of 

 the Norfolk coast, in the Musevim of the town of Norwich) evidence 

 of a part of the skeleton, of the rare and interesting extinct Cas- 

 torine animal, hitherto unknown and undescribed. This proba- 

 bility may engender in others, as in myself, a strong belief, if not 

 conviction, from the correspondence of the degTces of resemblance 

 and difl'erence which the femur in question presents, with those pre- 

 sented by the dentition of Trogontherium in the comparison with the 

 beaver [Castor Europceus), in which belief I assign this bone to Tro- 

 gontherium. 



The cervix femoris (PL III. Fig. 1, a, a.) is slender and sub-com- 

 pressed from before backward, the little that remains (the head 

 being broken off) indicates it to have inclined forward as well as up- 

 ward and inward, like the cervix femoris of Castor. The trochanter 

 major (ib. b), is a lofty three-sided process, with a large, rough, 

 convex summit, as in Castor, but it is relatively shorter, with a 

 broader base, and a deeper post-internal fossa (ib. c) Below the 

 fossa a low ridge extends towards the trochanter minor (ib. g), which 



