Description of a New Species of Gigantic Beaver-like Rodent. 29 
As to the general surface of the enamel, it has myriads of very 
minute shallow punctures and papille, coarser and finer, giving it 
a granulated or sandpapery look. 
Over all this, and dipping into the minutest inequalities of sur- 
face, is a brown film, hardly thicker than a coat of thin oo 
which I take to be cement. 
Some four to five inches from the apex is a line which appears 
to indicate where it was surrounded by the gum, and consequently 
the extent of projection beyond the socket. 
It only remains to speak of the beveled crown so characteristic 
of the rodents in general. It is two and one-eighth inches the 
longer way (fore and aft) and seven-eighths of an inch laterally. 
In general outline it would be ovate-oblong but for the gentle 
re-entrant curve caused by the sinus of the flatter side. It is an 
ivory face (bounded by a ring of enamel) as smooth as the bottom 
of a flat-iron and very nearly as flat. It is, however, slightly con- 
cave. Lay a straight-edge on the crown the longer way, and the 
face will be seen to sway away from it by about half a line near 
the middle of the basin. This face shows distinctly the gently 
curved line which is the outcrop of the plane dividing the tooth 
bilaterally from end to end.. 
There are also a few faint scratches on this ivory face, caused by 
the enamel of the antagonist incisor. The crown meets the ante- 
rior curve at an angle of about forty-five degrees. 
Toany specialists who may not be familiar with this specimen I 
have offered the above description in the hope to aid them in the 
study of it. 
And what were the zoological relations of the creature which 
once sported this incisor and which dwarfed even the Capybara of 
the present day and Castoroides ohioensis of the past? 
In the fluted, ribbed, corrugated, and granulated structure and 
appearance of this tooth, together with a peculiar way in which the 
ribs near the outer curve, as they extend backward, incline 
toward and lose themselves in the line of greatest convexity, one 
is continually reminded of Castoroides, to which genus it probably 
belongs. | 
But by no known principles of classification can I think it iden- 
tical with Castoroides ohioensis. Suffice it for the present to say 
that, on comparing it with the incisors, entire, of a specimen of C. 
ohioensis recently found in Randolph County, Ind., with two teeth 
