35 
Cases 8F and. O. — 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, 
SphceritUtes , Radiolites. Ijioceramus also belongs to this order, 
and sometimes reaches enormous size. 
Casts, much enlarged from the original, illustrating the forms 
of Formnmifera whose shells make up the vast deposits of chalk 
which characterize this period. 
Along with these deposits are flint nodules formed from the 
siliceous spicules of sponges, and many fossil sponges are pre- 
served — Sipho 7 iia, Cyclolites. 
West Wall of Hall 36. — Ventriculites are enormous sponges 
of this period. 
Case 9, Hall 36. — Among Echinoids, the free moving foims 
are vastly in excess of the stemmed — Holaster, Toxaster, and 
Aiianchytes. Among Cephalopods are specimens of the Nautilus 
of the modern type ; also members of the Ammoiiite family, which 
take on various and intricate forms, and many are of great size. 
All grades of shape are found, from the straight shelled to those 
of hook shape, partly uncoiled spirals, spirals, etc. The genera 
are named from their characteristic forms, some of them being as 
follows : Baculites, rod shaped, one specimen 3 ft. long. West wall 
of Hall 36; small Baculites ; Hamites, hook shaped; HelicoceraSt 
an open spiral; Macroscaphites, boat-shaped; Turrilites, tower- 
shaped. 
Agassiz describes these forms as representing the death con- 
torfions of this remarkable family. The term is an appropriate 
one, since with this age they become extinct. 
Lamellibranchs and GasteropodSy illustrated by many speci- 
mens, mostly of modern Xy^e^—OstreUy or oyster, of many and 
curious shapes, Fecteiiy Vola, Exogyra^ Gryphaeay etc. 
Nortli Wall of Hall 36. — Cast of head of Mosasaurusy 
the sea serpent of ancient times. This was a swimming, snake- 
like reptile, probably 80 feet in length. Its vertebrae are illus- 
trated by a cast. Case qE. 
Cases 9F, lO and 11. — Fossils of Cenozoic time, or age 
of mammals, divided into the Tertiary and Quaternary periods. 
Cases 9F, lO and 11 A and H. — Tertiary fossils. 
