GARMAN: THE CHIMAEROIDS. 255 
from the nourishing tissues and a continuous grinding away on the side toward 
the mouth cavity. 
The mouth of Rhinochimaera is narrower and more pointed than that of its 
fellows, probably in these respects approaching that of Rhynchodus, or of 
Rhamphodus, consequently its teeth are narrower and more elongate, Plate 5, 
Figures 1 and 2. Altogether the mouth resembles in a measure the beak of a. 
bird of prey; the teeth pass one another like the edges of a pair of shears and 
in front the vomerines are turned downward ina sharp hook. As the teeth 
are used entirely for cutting and holding and not for crushing, the stress comes 
on the sharp edges. The unassisted eye may hardly detect the existence of 
tritors, but with a lens, where the edges have been somewhat worn away, a 
series of the extremities of minute calcigerous tubes or pores is to be recog- 
nized. The dental plates are thin; in appearance they recall the horny fin 
rays, though they are not fibrous and are much harder and more brittle. The 
vomerines are small, convex outwardly, concave inwardly, in contact forward, 
hooked downward in front of the lower jaws, and feebly notched on the lateral 
cutting edge by contact with the mandibulars. The palatines are not in con- 
tact on the median line of the mouth; each of the pair is long and narrow, 
concave on the lower surface, blunt on the inner angle, slender and acute pos- 
teriorly, straight on the cutting edge except at the forward extremity where it 
curves upward, and but little bent upward on the inner edge. The man- 
dibulars are longer, more slender, and more pointed than the palatines ; they are 
concave on their upper surfaces, rounded instead of angled inwardly, slighily 
in contact at the symphysis, very little bent downward at the inner edges, and 
straight on the cutting edges except when curving down and inward below the 
vomerines. The only tritoral areas on these teeth are on the cutting edges. 
Probably the teeth of Rhinochimaera do not vary greatly from the type pos- 
sessed by the ancestral Chimaeroid, and 10 doubt the changes undergone in the 
teeth from very young to adult stages are comparatively slight. The indicated 
food of this Chimaeroid is crustacean and other life, of considerable depths of 
the ocean, in which the skeletons have no great degree of hardness. 
Harriotta, in most respects the nearest ally of Rhinochimaera, differs radi- 
cally in regard to the teeth, Plate 5, Figures 3, 4, 6-9. The dental plates are 
similar in shape and alike in number, but the tritors, even though they owe 
their existence to the common causes, stress and impact without perceptible 
differences in regard to exertion or reception, differ in arrangement from those 
of any other known Chimaeroid either fossil or recent. The mouth being 
wider in this genus than in Rhinochimaera and the function depending on the 
side of the tooth, rather than on the edge, the teeth are broader and much 
less sharpened at their extremities. The vomerines are of moderate size, 
somewhat broad, convex outward, concave inward, slightly hooked down in 
front of the mandibulars, and bear a marginal series of small tritors about 
nine in number. They are in-contact forward, and rather widely separated 
backward on the median line. The palatines are broad, broadly rounded in 
front and at the inner angle, more or less sharp posteriorly, and bear more or 
