716 POLYGONODON.—HADROSAURUS. 
a third has its convexity two inches wide, and twenty-one lines high. The spinal 
canal, preserved in two of the specimens, has a semi-circular form in transverse 
section, and measures nine lines wide, and six lines high at the entrance. 
POLYGONODON. 
Polygonodon vetus. 
Polygonodon vetus, Lerpy, Proc. Acad. Nat. Sci., 1856, VIII, 221. 
Polygonodon rectus, Emmons, Report North Carolina Geological Survey, 1858, 218, Fig. 27, A.; Manual of Geology, 
1860, 208, Fig. 3. 
Mossosaurus rectus, Emmons, North Carolina Geol. Sury., 1858, 218. 
The name of Polygonodon vetus was founded on a remarkable specimen, consist- 
ing of a shed tooth, from the Green-sand of Burlington County, New Jersey, from 
whence it was obtained by Lewis 'T. Germain, and was loaned to me for examina- 
tion by Prof. Cook. The specimen represented in Figs. 12, 13, Plate LX, consists 
of a nearly entire crown, wom at the apex and along the anterior and posterior 
borders. In construction it resembles the crown of the teeth of Mosasaurus, but is 
exceedingly narrow in comparison. It is in the form of a slender cone with the 
length more than three times the breadth of the base, compressed from without 
inwardly, and slightly curved inward and backward. It is nearly equally divided 
by acute ridges extending the length of the crown anteriorly and posteriorly. The 
ridges are much worn, so that it cannot be ascertained whether they were denticu- 
lated. The surfaces of the crown are subdivided into well-defined and 
No. 34 slightly unequal narrow. planes, there being seven externally and six in- 
{i8) ternally. ‘The enamel is quite smooth, though finely fissured longitudi- 
nally and jet black in the specimen. The transverse section, as represented 
in the outline, No. 34, is elliptical with acute poles. ‘The base is hollowed 
into a shallow funnel from a thick broken edge to a central pulp cavity, which is 
small, narrow, and of the shape of the crown. ‘The interior dentine is jet black 
and of dense structure. 
The length of the specimen is twenty lines; its width at base six lines by four 
lines and a half. The tooth may have belonged to Discosawrus or Cimoliasaurus, 
but the matter must be left for future determination. 
A specimen, identical in form and size with that just described, was found by 
Prof. Emmons on Cape Fear River, North Carolina, and was probably derived from 
the Green-sand. It is described and figured in the North Carolina Geological 
Survey, page 218, Fig. 37 (A). 
. 
HADROSAURUS. 
HMadrosaurus Foulkii. 
Hadrosaurus Foulkii, Lemy, Proc. Acad. Nat. Sci., Phila., 1858, 218. 
A remarkable reptile, of huge proportions, has been proved to have existed during 
the Cretaceous period of the Western Continent, to which the name of Hadrosaurus 
Foulkii has been applied. 
