56 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62, 
liquely and that the posterior root usually underlies the anterior root 
of the following tooth. 
A nearly perfect specimen of the last lower molar on the right side 
is represented in Figure 1, Plate 7. It conforms to the size and 
peculiar shape of this alveolus in the mandible, and there seems 
little or no chance for error in relegating the tooth to this position. 
Furthermore, it agrees in all essential details of form with similar 
last molars of previously described squalodonts.” 
The crown is low and roughly sculptured or covered with longitu- 
dinally striate enamel. The main cone or apex of the crown is 
depressed and bent backward. The anterior cutting edge slopes 
obliquely backward and is serrated by two low blunt accessory cusps, 
which incline in the direction of the main cusp, as well as by several 
small tubercles. On the posterior margin there are two well-defined 
cusps, one freely projecting and situated near the base of the crown, 
the other closely appressed to the main cone or apex of the tooth. 
The roots are short and stout. They are widely separated at the 
base and diverge rapidly, the anterior root being recurved distally. 
The serrulated cutting edges of the second left upper molar (pl. 7, 
fig. 2) conform to the type of tooth which would be needed to sup- 
plement the series shown by Leidy’s figure. The enamel surface is 
ornamented by a rugose network of striations which tend to assume 
a longitudinal arrangement on the apical portion of the crown. 
These striae are coarse toward the base and become finer toward the 
summit. The two accessory cusps on the anterior edge of the crown 
are restricted to the basal portion; they are low steplike and incline 
in the direction of the main cone. The three cusps on the posterior 
edge project freely and are provided with sharp edges. They are 
nearly equal in size. The apical half of the crown is not serrated 
by additional cusps, but the anterior and posterior margins exhibit 
indistinct sawlike cutting surfaces. The posterior root is longer and 
stouter than the anterior. The roots are connected by a short thin 
isthmus at the base and do not diverge to any marked extent dis- 
tally. Cope remarks that the roots of the molars of his squalodont 
were connected by a thin lamina at the base. Squalodon atlanticus 
lacks this modification. 
An incomplete second upper molar (pl. 7, fig. 4) from the opposite 
side of the skull exhibits no additional features. The anterior half 
of the crown is broken off. 
The allocation of some of the following teeth must be regarded as 
more or less provisional, for all the alveolae can not be opened suffi- 
ciently to insert the roots of the teeth for their full length. Certain 
of the alveolae are obstructed or closed by fragments of the sur- 
82 Dal Piaz, G., Palaeontographica Italica, Pisa, vol. 6, pl. 26, fig. 3, 1900. 
