116 KANSAS UNIVERSITY QUARTERLY. 
Xiphactinus molossus Cope. + 
“The premaxillary is vertically oval, convex externally, nearly 
flat within, and more than half underlaid by the anterior lamina of 
the maxillary. The anterior or median margin is regularly convex, 
and exhibits no surface or suture for union with the bone of the 
opposite side. Its posterior margin extends obliquely backward 
to beneath the superior artfcular condyle of the maxillary, and has 
a ragged edge, though the suture is squamose. Its superior mar- 
gin is deeply inflected in front of the condyle, and then convex and 
thickened. The anterior margin is thick and rugose with tubercu- 
lar exostoses. There are but two teeth, which are very large, and 
directed obliquely forward; the first is two-thirds the diameter of 
the second. 
“The maxillary is a large laminiform bone, with the upper margin 
considerably thickened proximally, but much thinned distally. It 
is abruptly contracted at the distal two-thirds of its length, appa- 
rently for the attachment of a supernumerary bone. The extrem- 
ity 1s curved saber-shaped upward, and has an acute toothless 
edge. The teeth are: four small, five large, and eighteen small. 
These teeth, except the largest, have cylindric bases; the crowns 
(and bases of the latter) are shghtly compressed or oval; they are 
straight and regular, and lean backward. The middle one of the 
five is largest, being six times as long as the smaller ones, but little 
more than half as long as the large premaxillary or mandibular. 
“The mandibular rami are short and deep, and have but little 
mutual attachment at the symphysis. They are not incurved at 
that point, and were bound by ligament only. There is no coro- 
noid bone, andthe articular is distinct. *° * *» The tecth¥ane 
as follows: Two large—a transverse groove; three large; four very 
small; nine medium; and two very small—total, twenty. These 
teeth have straight cylindric crowns, with cementum without striz 
or facets. The larger are little compressed.” 
Xiphactinus thaumas Cope.* 
“The premaxillary is an obliquely oval or subpentagonal bone, 
the suture with the maxillary is not toothed, and the anterior or 
free edge is smooth, not tubercular as in the two specimens of 
X. molossus. There are but two teeth, of which the anterior is 
immense, and the second little more half its diameter. The max- 
illary 1s stout and supports in front four very small teeth; then 
three very large, of which the median is _ largest. 
*Cert, Vert.. p. 197. 
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