Cope.] [Jan. 5, 
PACHYRHIZODUS. 
Dixon’s Geology of Sussex, 1850, p. 374. 
This genus was established by Prof. Agassiz, on a jaw fragment from 
Sussex, England, with avery brief description. The Kansas remains 
resemble this fragment in their corresponding parts, and I refer them to 
the same genus for the present. 
The genus as seen in our fossils, is defined as follows : 
Muzzle flat; premaxillary bones rather long, with two large teeth to- 
gether, near the anterior end, behind the usual external series. Maxil- 
lary and mandibles with a single series of simply cylindric curved teeth. 
Mandibular rami closely articulated by ligament. 
The teeth in this genus bear a superficial resemblance to those of a 
mosasauroid genus. Their mode of succession appears to be as follows : 
The crown of the young tooth was developed in a capsule at the base 
of the crown, or on the inner side of the apex of the thick root. The ab- 
sorption which followed excavated both the former and the latter, but 
the crown was evidently first shed. Finally, the old root disappeared, 
and when the new one occupied the alveolus, it left a free separation all 
round, Finally, on the accomplishment of the full growth of the root, 
it became anchylosed to the sides of the alveolus. The pleurodont posi- 
tion of the tooth facilitated the shedding of the root very materially. 
The genus Conosaurus, Gibbes, from South Carolina, is, perhaps allied. 
to this one. Its dentition is fully described by Leidy, who changes the 
name to Conosaurops, mainly on account of the inappropriateness of the 
Greek Luvpos toa fish. This word was, however, employed by the an- 
cients to designate a fish, and the only use made of the word out of com- 
position, by modern zodlogists, is for species of that class, so that it does 
not seem improper to use it here.* 
Three, perhaps four, species left their remains in the strata examined 
by the expedition. 
PACHYRHIZODUS CANINUS. Cope. sp. nov. 
Established on portions of, perhaps, two individuals, which embrace 
one nearly complete maxillary bone, two premaxillaries of opposite 
sides, two nearly perfect rami of the mandible, with numerous other por- 
tions in a fragmentary condition. 
These indicate a cranium of about a foot in length, by six and a half 
in width, oval in outline, with moderately obtuse muzzle. The man- 
dibular teeth are directed somewhat outwards ; the premaxillary is hori- 
zontal in front, and the maxillary narrow. From these facts I derive 
that the head was probably depressed, as in the modern Sauri, and very 
different from the prevalent compressed form of the Porthed and allies. 
*The case appears to me to be different with the name Jschyrosaurus, which I proposed to 
replace with Jschyrotherium (Leidy). The latter was given to a genus of saurians, under the 
supposition that it belonged to the mammalia, and the termination, theriwm, devoted to this 
group of animals by meaning and custom, cannot be applied toa sauriam by any stretch of 
metonymy or charity, 
