0. C. Marsh—Dermal Scutes of Mosasauroid Reptiles. 291 
genera,* and the same party, during their investigations of the 
past year in that region, have added several other important 
their true affinities. An examination of a large number of 
specimens has shown that this covering existed in Hdestosaurus, 
jodon, Holeodus and Clidastes, and hence there can be little 
doubt that it was common to the entire group. 
The plates were first observed in a specimen of Hdestosaurus, 
on which several were adhering to portions of the skull and 
lower jaws. A few of these were attached together, a ps 
in their original position with reference to each other, thus 
indicating their natural arrangement. There were evidently at 
least two or three kinds of scutes, and all of those preserved are 
essentially quadrilateral in form, the posterior margin being the 
shortest. the lower surface is smooth. The upper side has 
the margin more or less beveled, to admit an imbricate arrange- 
ment when in place, but no true ornamentation. The edges are, 
in general, quite thin, but one shows that it was unit 
sutur ere are also indications of an imperfect articulation, 
somewhat like that seen in the plates of some species 0 
Paleoniscus 
Measurements. 
Length of large scute of Hdestosaurus, ------------------ 5 li 
Width at anterior margin, ---.-_------------------ ----- Me fh 
Width at posterior margin,.il.5..2 (ss esse este ake + eee 9° 
Greatest thickness ¢2o¢ .asrut Jsoieere es Le - 3° 
a of small scute of Hiestosaurus, . -------- jodhe ie sh 18° 
Wi h at anterior Margin, - —-6 Js c1 005 Gsi- 46 Oe ON oe Se 18° 
Width at posterior MAPgIN, Jou 5 dec wn der aeisssmen Ahine e- 12° 
OSE I Rall aatihd ea SEs ail HS SEP 5 
In the genus Liodon, the scutes are acne gree and some- 
. . ' b 
to be proportionally smaller. Those found with one specimen 
are quadrilateral in form, with the posterior margin shortest. 
ey are smooth below, but the upper surface 1s rugose. The ex- 
posed portion is linguiform, with its longer axis corresponding to 
that of the seute. One perfect scute was 269", 4n length, 20 in 
average width, and 4-25 in thickness. The scutes in Holcodus, 
* This Journal, vol. i. p. 447, June, 1871. 
tl 
