field AlUSEUM OF NATURAL HISTORY 
meiUioned .JSschna and Pctalia, dragontlies; Bclostonunii, an 
ant ; Nepa, a water bug. 
Fishes of the Jurassic are represented (Hall 36) by a large 
number of specimens from England, Bavaria, and Wurtemburg. 
These are chiefly of two types. The Ganoids, which were the 
predominant type, may be recognized by their heavy, angular 
scales. The following genera are well represented: Catiinis, 
AspidorhynchuSy Thrissops, Lcptolcpis and Dapedius. The Sela- 
chians or sharks, having neither bony skeleton nor scales, are 
represented by the teeth and fln-rays only. Some genera of this 
t}’pe shown are Acrodus, Hybodus and Chondrosteus. 
Ichthyosaurs, from the Jurassic of England and Germany are 
represented (Hall 36) by an unusually fine series of skulls and 
skeletons. The Ichthyosaurs, or fish-lizards were a type of marine 
reptile having a fish-like body and tail, a short neck, a long, 
pointed snout, enormous e 3 ^es and paddles somewhat like those 
of a seal. They attained a length of twentyTve to thirty feet. 
A model exhibited on the floor shows something of their out- 
ward appearance. 
A second form of marine reptile common to this period is that 
of Plesiosaurs. These were more slender and graceful animals 
than the Ichthyosaurs. Some forms had a ver}^ long neck. The 
body was short and armed with stout, paddle-like legs which 
were used in swimming. In the long-necked Plesiosaurs the 
head was broad and snake-like; in the short-necked types it 
ended in a slender snout similar to that of the Ichtlwosaurs. A 
model of one of the long-necked types exhibited on the floor 
of Hall 36 will give some idea of the general proportions of some 
of these animals. 
Cretaceous Period. — IModels (Hall 59) much enlarged from 
the original, illustrate the forms of Foraminifera, whose shells 
make up the vast deposits of chalk which characterize this period. 
Sponges are shown in many forms. Some of these served as 
nuclei for the formation of flint nodules. Several large nodules 
of this kind are shown from Ireland. 
Echinoids are illustrated b>" AnancJiytes, Houiastcry Holastcr, 
LinthiOj Toxaster, etc. 
The Crinoids of the period are magnificently illustrated in a 
large framed slab placed on the wall of Hall 36. This slab is 
