31 



of great size. The specimens show their appearance 

 at the dawn of geological time as straight shells with 

 simple concave partitions or septa ; their gradual 

 development into bent, then curved, then coiled 

 forms; then the change from simple to highly corru- 

 gated septa, with other changes ; their period of 

 prominence; and finally their decline, whec they again 

 assume the straight forms of their youth, though 

 maintaining the internal structure of the adult. At 

 the end of the Tertiary they become suddenly ex- 

 tinct } and are to-day represented only by one of the 

 early type forms which survived — the Nautilus. 



Rocky Mountain Goat, ete. — This case contains some 

 of the hoofed animals to be met with in the Rocky 

 Mountain region. Here is the long-haired goat, and 

 the much better known big horned sheep. This is 

 the animal about which such tales are told of marvel- 

 lous leaps from perpendicular cliffs, the truth or fal- 

 sity of which does not yet appear to be settled to the 

 satisfaction of everybody. With them is the prong- 

 horned antelope, the only antelope found on this con- 

 tinent. The antelopes stand between the goats, and 

 the deer, differing from the latter 5 among other things, 

 in that the horns are hollow and perennial. They 

 are among the most graceful of animals. 



