32 
such as Sassafras, Populites, or poplar, Betulites, or birch, and 
Viburnum . 
Cases 8F and G.— Among bivalve mollusks the order of 
Rudistes is unique, and characteristic of this period. In shells of 
this order one valve is enormously enlarged, and somewhat funnel- 
shaped ; the other valve is small and acts as a lid — Hippurites, 
Sphoerulites , Radioiites. Inoceramus also belongs to this order, 
and sometimes reaches enormous size. 
Casts, much enlarged from the original, illustrating the forms 
of Foraminifera, whose shells make up the vast deposits of chalk 
which characterize this period. 
Case 9, Hall 36.— Among Echinoids, the free moving forms 
are vastly in excess of the stemmed — A nanchytes, Holaster , and 
Toxastcr . Among Cephalopods are specimens of Nautilus of 
modern type ; also members of the Ammonite family, which take 
on various and intricate forms. Many varieties of shape are 
found, from straight-shelled to hook-shape, partly uncoiled spirals, 
spirals, etc. The genera are named from their characteristic 
forms, some of them being as follows : Baculites , rod-shaped; 
Hamites , hook-shaped ; Helicoceras , an open spiral ; Scaphites , 
boat-shaped ; Turrilites , tower-shaped. 
Agassiz describes these forms as representing the death con- 
tortions of this remarkable family. The term is an appropriate 
one, since with this age the group, which had so long been one of 
the dominant types of marine life, became extinct. 
Lamellibranchs and Gasteropods , illustrated by many speci- 
mens, mostly of modern types — Ostrea, or oyster, of many and 
curious shapes; Pecten , Vola, Exogyra , Gryphcea , etc. 
A fine series of fossil leaves from the Upper Laramie, Golden, 
Colo., is placed here. 
North Wall of Hall 36. — Cast of head of Mosasaurus , 
the sea serpent of ancient times. This was a swimming, snake- 
like reptile, probably eighty feet in length. 
Cases 9F, 16, and 11. — Fossils of Cenozoic time, or age 
of mammals, divided into the Tertiary and Quaternary periods. 
Cases 9F, lO and 11 A 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. 
