26 FIELD MUSEUM OF NATURAL HISTORY 
numbers in the chalk beds of western Kansas; also in Eng- 
land and Belgium. They are represented in the collection 
chiefly by a complete skeleton of Platycarpus from Kansas 
(Hall 59.) 
Plesiosaurs were a second type of marine reptile which, as 
has been mentioned, appeared in the Jurassic period and con- 
tinued to the close of the Cretaceous. The specimen of Elas- 
mosaurus is of interest in showing the shoulder and pelvic girdles 
in connection with a complete paddle. (Hall 59.) 
Pterodactyls, or flying reptiles, represent one of the strangest 
forms assumed by reptilian life toward the close of the Mesozoic 
era. They were very slight and active creatures, somewhat bat- 
like in general appearance, but withal distinctly reptilian. The 
head was armed with a stout, bird-like beak, the bones were 
hollow, the wing-bones were long and supported a membrane 
which connected with the legs, thus forming the organ of flight. 
In powers of flight they doubtless equaled any of the existing 
birds. The group is represented by a splendid skeleton of Nyc- 
tosaurus from the chalk beds of Kansas. This is the most com- 
plete specimen known. Other related forms have been found 
in various parts of Europe. (Hall 59.) 
Turtles of this 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. In this period true bony fishes of modern types 
made their first appearance. A number of these from Lebanon, 
Syria, as well as some American forms are exhibited. 
Other fossils of the Cretaceous period shown include remains 
of plants and invertebrates as follows: 
The first of modern plants, or Angiosperms. Imprints of 
eaves are shown, many being of modern genera, such as Sas- 
safras, Populites or poplar, Betulites, or birch. Viburnum, Ilex, 
or holly, Magnolia, etc. 
The localities represented are chiefly Kansas and Colorado. 
Models 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 by Ananchytes, Holaster, Toxaster, 
