26 
modern type; also members of the Ammonite family, which take 
on various and intricate forms. The series of P lac entic eras. Am- 
monites with c oiled shells often two feet in diameter, is especially 
worthy of note. The specimens are chiefly from the Bad Lands 
of South Dakota. Many varieties of shape are found among the 
Ammonites, from straight shelled to hook-shape, partly uncoiled 
spirals, spirals, etc. The genera are often named from their char- 
acteristic forms, some of them being as follows ; Baculites, rod- 
shaped; Haijiites, hook-shaped; Helicoceras an open spiral; 
Scap kites, boat shaped ; Turrilites, tower-shaped. 
Agassiz describes these forms as representing the death con- 
tortions of this remarkable family. It is true that with this age 
this group, which had so long been one of the dominant types of 
marine life, became extinct, but the forms show progression up 
to the time of extinction, and not degeneration. 
Lamellibranchs and Gasteropods, illustrated by many speci- 
mens, mostly of modern types — OUrea, or oyster, of many and 
curious shapes ; Pecten, Vola, Exogyra, Gryphcea, etc. 
Fossil leaves from the Upper Laramie beds of Golden, Colo. 
These are of deciduous trees of modern type, such as poplar and 
oak ; also the fig. 
The vertebrates of the period are represented by a tail of 
Xiphactinus and fin of Pelecopteris huge, carnivorous fishes, and 
by a skull of Liodon, a carnivorous sea lizard. All of these in- 
habited the Cretaceous seas of Kansas. Casts show the remains 
of a Mososaurus from Holland, a sea lizard probably 8o feet in 
length, and of Hesperornis, one of the earliest birds. 
Cases 9F, 10, and 11. — Fossils of Cenozoic time, or age of 
mammals, divided into the Tertiary and Quarternary periods. 
Cases 9F, 10 and llA and B. — Tertiary fossils. 
Case 9F. — Flabellaria, leaves of a palm which grew in the 
Eocene epoch near Green River, Wyoming. Also, leaves of Acer, 
or maple, and other trees of modern species. 
Such remains, with others that are found, indicate that a sub- 
tropical climate, like that of Florida, prevailed at this period over 
the Northern United States. Even as far north as Greenland, the 
climate was so mild that cypress and cedar trees grew in profusion. 
Nummulites. — These are abundant and characteristic fossils 
of this period. They are shells of a Rhizopod, which in Europe 
and Africa form limestones many thousand feet in thickness. 
