DEPART.AIENT OF GEOLOGY 
10 
The huge frog-like head of Lahyvinthodon shown by a cast 
is that of an Amphibian, and the Reptiles of the period are rep- 
resented by a cast of a head of Belodon, an ancient crocodile. 
Hall 35. 
This hall contains two somewhat distinct series, one intro- 
ductory to the study of fossils in general, the other, fossils of the 
Mesozoic era. 
Entering the hall from the West Court, the three wall cases 
on the right are devoted to the introductor}" series. The first 
two of these show a comparison of ancient and modern forms. 
Beginning with the lower orders of life, there are shown, for ex- 
ample, Sponges which have lived at different periods of the 
earth s history, and a modern sponge for comparison ; while in 
succession corals, crinoids, brachiopods, articulates, and verte- 
brates are similarly illustrated. 
In the third case of the series, methods of fossilization are 
illustrated. The methods shown include preservation of hard 
parts, as shells and bones, internal moulds, external moulds, 
impressions and illustrations of incrustation, carbonization, silici- 
fication, phosphatization, etc. 
The fossils of the Mesozoic era represented in this hall are 
chiefly the Dinosaurs of the Jurassic period. The Jurassic dino- 
saurs were great shore reptiles; they were the largest land ani- 
mals that have ever been discovered. Among animals they are 
exceeded in bulk onD by the great right-whales of modern times. 
The specimens exhibited were collected b}’ special expeditions 
sent by the Museum for this purpose to Wyoming and Colorado. 
The central exhibit is a partial skeleton of one of the largest 
dinosaurs known. Apatosaurus. Onh* a little more than half of 
the skeleton is here represented. The head, neck, shoulder gir- 
dle, fore legs and the extremity of the tail are wanting entirely. 
The right hind leg below the knee is copied in plaster from other 
similar specimens. The left is modeled entirely from the right. 
The portion of the skeleton exhibited was found with all of 
its parts connected and has been carefully mounted in its natural 
position. Therefore, the body of the animal, the pelvis, the 
hind legs and the greater part of the tail are accurately repre- 
sented in their natural relations. 
