DEPARTMENT OF GEOLOGY 
23 
x4 feet in size and is covered with the bodies of Crinoids, 200 
nearly complete individuals being shown. 
Pelecypods and Gastropods are. illustrated by many speci- 
mens, mostly of modern types, such as Ostrea, Exogyra, and 
Gryphcea, which were Oysters of many and curious shapes, and 
Pectens, Vola, etc., which were Scallops. 
Among bivalve molluscs the family of Rudistae is unique, 
and characteristic of this period. In shells of this family one 
valve is enormously enlarged, and somewhat funnel-shaped ; 
the other valve is small and acts as a lid. Hippurites, Spheru- 
lites and Radiolites belong to this family. Inoceramus sometimes 
reached enormous size. 
Among Cephalopods are shown specimens of Nautilus of 
modern types and members of the Ammonite family which 
took on various and intricate forms. The series of Placenticeras, 
an ammonite with coiled shells often two feet in diameter, is es- 
pecially worthy of note. The specimens are chiefly from the 
Bad Lands of South Dakota. Many varieties of shape are 
shown from straight shells to hook-shaped, partly uncoiled, 
spirals, etc. The names of the genera often indicate character- 
istic forms, such as: Baculites, rod-shaped; Hamites, hook- 
shaped; Helicoceras, an open spiral; Scaphites, boat-shaped; Tur- 
rilites, tower-shaped. 
Fossil plants which were the first of modern types are il- 
lustrated by leaves of Sassafras, Populites, or poplar, Betulites, 
or birch. Viburnum, Ilex, or holly, Magnolia, etc. 
Turtles of the period are represented by the shell of a large 
fresh water form, Basilemys. This was found in the latest Cre- 
taceous beds of Montana. 
Fishes of the period are seen to be of modern types. A num- 
ber of these from Lebanon, Syria, and some American forms are 
exhibited. 
Other vertebrates of the Cretaceous period are represented 
by specimens of Dinosaurs, Plesiosaurs, Pterodactyls and Fishes. 
They are of different types from those of the Jurassic. 
Cretaceous Dinosaurs are illustrated by a fine skull and par- 
tial skeleton of Triceratops and a restoration of the skeleton 
of Hadrosaurus (Hall 36). Triceratops was a unique armored 
land reptile of gigantic proportions and the specimen shown is 
one of the largest of its kind. It was collected in eastern Mon- 
