No. 1.] MORPHOLOGY (OF CLADOSELACHE. EO7 
not marked in the symphysial rows. The development of 
the lateral denticles, outer and inner, as we pass to the 
angle of the mouth, leads naturally to a condition that is 
strikingly hybodont. (Cf. Synechodus.) Hybodont, too, is 
the fact that (1) the marginal rows are the smaller and rounder 
and more degenerate in cusp characters, and (2) that the greatest 
wearing line appears to fall upon the middle members of each 
bank. The teeth typical of C/adodus occur in the rows of the 
anterior third of each jaw; here the length of the lateral 
denticles is about one-half that of the main cusp. Incurving of 
teeth is most marked in the front of the mouth, the direction 
of cusp becoming nearly parallel to its broad base. Underlying 
teeth appear to assume the s-like form. Teeth in the region 
of the mouth angle, become slightly unsymmetrical. Entire 
specimens, which represent perhaps young animals, show little 
abrasion of cusps. The teeth of an entire mouth of a large 
individual of Cladodus (?) terrelli indicate that wearing action 
had been greatest little more than midway from symphysis of 
jaw to articulation, —the pointed cusps, stout heavy ones in 
most cases, being ground away to their bases ; and the appear- 
ance of the entire jaw is in consequence decidedly hybodont, 
none the less so as the teeth of jaw margin and mouth angle 
became small and bluntly chisel-like. 
There appears to be present in Cladoselache no shagreen 
denticles at the outer margin of each jaw, which might be 
mistaken for teeth. 
Eyes and nares are prominently marked in nearly all speci- 
mens. The olfactory capsules were terminal, large, and seem 
to have been placed quite closely together. The orbits were 
placed well forward in the head, the capsules appearing to be 
larger proportionally than those of Chlamydoselache. 
Chlamydoselache may be looked upon as representing one 
type of Cladodont dentition. It does not agree with that of 
Cladoselache in a number of important characters. Its teeth, 
for example, are small, uniform in shape, decreasing in size 
from the middle line to mouth angle, and from the outer to the 
inner rows, each row with an alley-way separating it from its 
neighbor, each lateral denticle almost as serviceable as a 
