FLOOR.] 
FOSSILS. 
27 
The small Table Case under the window contains leaves of Dicotyle- 
donous Plants, from the Tertiary Limestone of (Eningen. 
The slabs of Sandstone on the North Wall of this Room, with the 
tracks of an unknown animal, called Chirotherium, probably amphi- 
bious, with large hind feet, like some Batrachians, are, that on the 
left, from the quarries of Hildburghausen, in Saxony; and that in the 
centre, from Stourton Hill quarry, near Liverpool (the latter pre- 
sented by J. Tomkinson, Esq.). On the right hand are placed slabs 
also supposed to be of the New Red Sandstone formation, with equally 
remarkable impressions of various dimensions, called Ornithichnites, 
being regarded as the foot-marks of birds. They occur in the Sand- 
stone beds near Greenfield, Massachusetts, at Turner's Falls, in the 
Connecticut River. Other slabs from the same locality, and also 
from Cheshire and Staffordshire, covered with reptilian footprints, 
are placed on Wall Cases 1. and 11 of Room III. 
ROOM II. 
The classification of the Fossil Fishes, arranged in this room, is 
chiefly in accordance with that proposed by M. Agassiz, in his great 
work, entitled "Becherches sur les Poissons Fossilcs" with some mo- 
difications founded upon the later systems proposed by Professors Miiller 
and Owen. The series commences with the Placoid Fishes, or those of 
the Shark and Ray tribes, in which the skin is protected by rounded 
(often star-shaped) and very hard scales, having frequently a raised 
point, and sometimes a thorn-like prickle in the centre, as may be 
seen in the scales of the Thornback and some other fishes of the 
Skate tribe. The upper division of the tail is prolonged beyond the 
lower lobe, and is supported by a continuation of the vertebral 
column — a form of tail which is termed Hetero cereal, and which is 
most commonly found in all the orders of fishes of the middle and older 
Geological formations ; but which (if we except the Sharks and Rays) 
is rarely met with in the existing species of fishes, in which the " ho- 
mocercal " tail, or that with the two lobes equal, prevails. 
The skeleton of the Placoids being more or less gristly, and in the 
same degree perishable and incapable of fossilization, the remains of 
those fishes consist chiefly of the defensive spines, scales, and teeth ; 
these objects, being mostly of small size, will be found in the Cases 
under the windows, and in Case 7 at the end of the room. 
The Fishes called Ganoids have derived their name, and the 
character of their order, from the lustre of their very hard, enamelled 
scales; and it is by these parts that they are chiefly represented in 
the fossil state. The most common form of scale in this order is the 
rhomboidal, in a few it is round ; but the pattern of the external mark- 
ings varies in almost every species. 
Ganoid Fishes range from the newest Silurian strata upwards ; are 
most abundant in the lower Oolitic formations, diminish in the cre- 
taceous beds, and are reduced to very few genera existing at the present 
time. 
