265 
1871.J {Cope. 
We have additional species from 
Carolina Mosasamius)cst, soles toot ns Seiraensis vise occas iL 
Mississippl (Platecampus)aais sins oes sry eee. Tie eee 1L 
Nebraska (Mosasaurus)...........- on soe SSRI ae AlEssisae i 1 
making with the others from 
ENG UGESO VR. a. 8) SSE EN. elicits ha bk wees sie. ais 15 
Alabama 20. caine eee uae ts. bin oud eye eek i: 7 
ISADSAS. ofa Nia leos. Sac tle os aucls anise ties SN eases ek 17 
aA TO tall Ole oe? ian ete sous pity stin Bis Wiearsciee a sale es oes 42 
Of these I am not acquainted with any which extends its range into 
any two of the areas above named, while some of the districts possess 
peculiar genera. It is nevertheless premature to draw any conclusions as 
to geographical range, as most of the species are known from but few 
specimens as yet. 
Two genera have recently been discovered in Europe, which have been 
thought to be allied, or belong, to this order. One of these, Acrodon- 
toswurus Hulke, rests on the anterior portion of a maxillary bone with 
part of premaxillary and teeth. These portions are indecisive as to its 
affinities. It is from the English Chalk. The second form is the Danu- 
dtosaurus of Bunzel, which its describer refers to the neighborhood of 
Mosasaurus. It is quite plain after an inspection of his description and 
‘figures, that it has no affinity to that genus or to the order Pythonomor- 
pha. Itis from Neue Welt, from the Cretaceous, near Vienna. 
The present investigations have added some points of importance to 
the history of the structure of the order. 
First, as to the pterygoid bones. It appears that these elements are 
thin plates, having a free laminar termination, and are entirely toothless. 
They articulate with the palatines by a process which fits their posterior 
emargination. In Hdestosaurus tortor, they are about half the length of 
the palatines. They present no indications of ectopterygoid. The bones 
named by authors pterygoids, in imitation of Cuvier, are elongate pala- 
tines, and the external process extending to the maxillaries, is that seen 
in Varani, serpents, etc., and is at no time distinct from the palatines. 
It has also shown that the supposition of Goldfuss and myself, thatthe 
palatines of Mosasaurus were in contact on the median line, is an error, 
and that they are more or less vertical plates, as in Liodon. The dis- 
tinction between these genera, then, rests on the codssification of the 
chevron bones in the former, and their permanent independence in the 
latter ; perhaps the difference in the form of the teeth may also count for 
something. 
Second, as to the parieto-squamosal arch, which is distinctly developed 
in Holcodus tctericus and Liodon curtirostris in its parietal part and ZH. 
_ corypheus in the squamosal part. It was quite strong in the species 
named. 
Third, as to the pelvis. This part, which has been observed by Marsh 
A. P. S—VOL. XII—2 
