38 
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, 
SphcEruliteSy Radiolites. Inoceramm also belongs to this order, 
and sometimes reaches enormous size. 
Casts, much enlarged from the original, illustrating the forms 
of Fo 7 'a 7 )ii 7 iifera 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 — Siphoiiiay Cy do Hies. 
West Wall of Hall 3G, — Ventriculites are enormous sponges 
of this period. 
Case 1), Hall 30. — Among Echinoids, the free moving forms 
are vastly in excess of the stemmed — Holaster, Toxaster, and 
A^ianchytes. Among Cephalopods are specimens of Nautilus of 
modern type; also members of the Anwio^iite family, which take 
on various and intricate forms. 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 character- 
istic forms, some of them being as follows: Baculites, rod-shaped, 
one specimen 3 ft. long. West wall of Hall 36; small Baculites\ 
Hamites, hook-shsiped ; //elicoceras, a.n open spira}; Macroscap^ites, 
boat-shaped; Tuj'rilites, 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 they become extinct. 
Lmnelhbranchs and Gasteropods^ illustrated by many speci- 
mens, mostly of modern types — Ostrea, or oyster, of many and 
curious shapes, Pecte^iy J^o/a, Exogy7‘ay GryphaeUy etc. 
Nortli Wall of Hall 30 . — 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 9E. 
Cases 9F, lO and 11. — Fossils of Cenozoic time, or age 
of mammals, divided into the Tertiary and Quaternary periods. 
Cases OF, lO and 11 A and H. — Tertiary fossils, 
