DEPARTMENT OF GEOLOGY 
17 
from near Burlington, Iowa, is shown in the floor case in Hall 
36, at the right of the entrance from Hall 35. 
Other genera, shown in the regular order in Hall 33 are 
PlatycrinuSj Batocrinus, Actinocrinus, AgaricocrinuSj etc., rep- 
resented by many species. Those specimens having the arms 
and stems attached are of particular interest. 
Pentremites, Cryptoblastus, SchizohlastuSj Granotocrinus, etc., 
are typical Blastoids, or bud-like animals, near relatives of the 
Crinoids which flourished at this time. 
Large slabs of Melonites, an ancient Sea-urchin, are shown. 
These echinoderms differed from the modern forms in the 
greater number and smaller size of the plates. 
Corals are on the decline, but such genera as Zaphrentis, 
Lophophyllum, Cyathophyllum and Lithostrotion occur and are 
shown. 
The corkscrew-like Bryozoan Archimedes is illustrated by a 
number of species. 
Such Gastropods as Straparollus, EuomphaluSj Bellerophon, 
Pleurotomaria, Naticopsis, etc., are still abundant. 
The plain-sutured Nautilus and the zigzag-sutured Gonia- 
tites are the principal Cephalopods. 
The Trilobitesi have disappeared and in their place is shown 
Euprops which somewhat resembles the horse-shoe crab. 
Pennsylvanian Period or Age of Coal P/awf.r.— Land plants 
are the striking features of this period. They are allied to the 
four modern groups of Ferns, Lycopods, Conifers and Horse- 
tails. 
The Ferns surpassed all other land plants in number. Pecop- 
teris, Neuropteris, AlethopteriSj etc., are shown both as single 
leaflets and fronds. Many of these have been preserved in the 
center of clay concretions and are shown in a number which 
have been broken open. 
Lepidodendron and Sigillaria are shown by sections of trunks 
and by impressions of the bark. The size of some of the stumps 
of Sigillaria shown indicates that the original tree must have 
attained a height of 80 or 100 feet. Stigmaria probably repre- 
sents the under water stems of Sigillaria or Lepidodendron, 
These were similar, except in size, to the modern Lycopods, or 
Club-mosses. 
