Dein of a New Species of Gigantic Beaver-like Rodent. 27 
reater diameter, fore and aft, near apex, . PE e/eelGeches: 
Wesser diameter, right and left, at base, . : iia 
Lesser diameter, midway, . : ; ye aI a eos 
Lesser diameter, across beveled crown, . ei inicln: 
Length of beveled crown, fore and aft, negates: 
@ircumference at base, . wedOdte ye oe 
Gireumference at middle, . ; : aso tee 
Circumference at distal end, . eee ag hin 
Standing the tooth on its base and apex, the hee Si 
the arch is Eee BOw Nee 
The curvature at pee Sane alone the median line would appear 
to be very nearly an arc of say one hundred and sixty degrees of a 
circle whose radius 1S six inches. On measurement, however, it 
was found to have a more rapid curvature as we approach the 
outer extremity. The proximal side, that which faced its com- 
panion incisor, is approximately flat as compared with the distal 
side, which approaches to semi-cylindrical. The flatter side is by 
no means mathematically flat. It has a shallow valley-like 
mesial groove extending from end to end very near the middle, so 
that a section at any point would give us an outline similar to that 
of alima bean. ‘The sinus is about one-eighth of an inch deep, 
as measured by laying a straight-edge from ridge to ridge on either 
side. Said sinus has a corresponding ridge on the opposite wall of 
the hollow base, almost the whole length of the pulp cavity; 
though the ridge on the inside is not so well defined as the sinus 
on the outside. 
This whole specimen has a fresh look about it, which tends to 
dissipate the idea of its being a fossil. The two cross breaks and 
the cleft base give amp!e opportunity to study the ivory, enamel, 
and the pulp cavity. The ivory hasa clean, creamy look, showing 
the grain, the mode of growth, lamine, etc. 
The pulp cavity is eight and one-fourth inches long, following 
the curve. The thickness of the wall is reduced to a mere blade 
at the base, but thickens gradually outward as the cavity narrows. 
This cavity is nearly flat on the side corresponding to the flatter 
side of the tooth, and semi-conical on the other. 
The enamel invests the entire body of the tooth, showing all 
around the border of the beveled crown and around the borders of 
the sections, one of which is three and a-half inches from the apex, 
the other near the middle. 
