ant. 16, TWO SQUALODONTS FROM MARYLAND—KELLOGG. 57 
rounding bone which piece the walls of the alveolae, and all are 
filled in with the surrounding matrix. The specimen is so fragile 
that an attempt to remove these obstructions would probably result 
in serious damage to the skull and mandible. However, in so far as 
conditions permitted, the teeth have been fitted to their respective 
alveolae where present. 
The second lower molar (pl. 7, fig. 3) on the right side is charac- 
terized by a high and poimted crown which lacks accessory cusps on 
the anterior margin. The enamel surface exhibits the same orna- 
mentation as the other molars. The posterior margin bears two 
closely appressed accessory cusps. The roots are long and at the 
base are connected by a short thin isthmus. The posterior root pro- 
jects more downward than backward, and the anterior root recurves 
distally. 
In considering the premolars certain features are apparent at 
first glance. The crowns are shorter and the roots approximate 
each other more closely than in the molars. They are characterized 
by high compressed crowns and are provided with sawlike cutting 
surfaces on the anterior and posterior edges. One of these, the 
fourth upper premolar on the left side (pl. 7, fig. 5), bears two well- 
defined cusps on the posterior margin. The roots of the premolars 
are connected by a thin isthmus of varying extent. In the above- 
mentioned tooth the distal one-third of the anterior root is free, while 
only the very tip is not so united in the fourth right lower premolar 
(pl. 7, fig. 7). The curvature of the crown and the appearance of 
the enamel of the third right lower premolar (pl. 7, fig. 6) is essen- 
tially the same as the others. 
The posterior roots of the premolars tend to become bent back- 
ward. The roots are relatively very long, and the oblique position 
they assume in the alveolae of the shallow jaws does not allow a 
deeper implantation than the inferior dental canal, and in consequence 
the ends of the posterior roots are forced to assume a horizontal 
position. 
Four teeth (pl. 8, figs. 1-4) remain to be discussed. Notwithstanding 
the general resemblance of these teeth to the incisors, there appears 
some difficulty in deciding whether one or more may not represent 4 
canine tooth. They all possess compressed and slightly recurved 
crowns. The enamel is longitudinally striate and the cutting surfaces 
are sharp edged. The roots are long and curve backward. A close 
examination of the curvature of these four teeth and a comparison 
of the positions they assumed when inserted in the alveolae of the 
skull and mandible resulted in assigning three of them to the upper 
jaws. If this determination is correct, then one (pl. 8, fig. 1) prob- 
ably represents a lower canine tooth. 
