TROGONTHERIUM CUYVIERI. 187 
Jromer. The stratum of clay is eight feet thick, and con- 
tains pyrites: its upper part is at about high water-mark, 
and it forms the beach. Here, or in situ in the blue clay, 
were discovered bones of the Mammoth, Rhinoceros, Ox, 
Horse, and Deer. 
The Trogontherian relic is a portion of the right ramus of 
the lower jaw, contaming half the root of the great in- 
cisor, and the three anterior molar teeth cn situ. The 
proportions of these teeth differ conspicuously from those 
in the Beavers, both European and American. The an- 
tero-posterior and transverse diameters of the first grinder 
exceed by one-third those of the second grinder: both 
the second and third molars are smaller in proportion to 
the incisor than in the Beaver; and the socket of the 
fourth tooth shews this to have had a longer antero-poste- 
rior diameter than the third grinder, which is the reverse 
of the proportions of these teeth in the genus Castor, The 
grinding surface of the first molar, 1m, which alone bears the 
same proportion to the incisor as in the Beaver, has the 
same number and general direction of enamel-folds, viz. 
four,—three continued from the inner side of the tooth, 
and this extends further into 
and one from the outer side, 
the substance of the tooth than in the Beaver, at an age 
when the molars are as much worn down as in the present 
specimen. The two succeeding grinders of the T’rogonthe- 
rium differ in a more marked degree from the correspond- 
ing teeth in the genus Castor, having but two inflected 
folds of enamel, one from the outer, the other from the 
inner side of the tooth; the latter also being relatively 
longer than the single inner fold of enamel in the Beaver’s 
grinders, all of which retain the three outer folds of enamel. 
The opportunity of instituting these comparisons is the 
more valuable, since M. Fischer has not entered into the 
