20 FIELD MUSEUM OF NATURAL HISTORY 
Cordaitcs appears to be allied to both the Conifers and the 
Cycads. It had a straight trunk 6o or 70 feet in height and long 
narrow eaves. Trigonocarpmn Sind Car diocarpurm.vQ 
to be the fruit of this tree. 
Catamites, Annularia, etc., are allied to the Kquisetum or 
modern Horsetails. Stems of the former and leaf whorls of the 
latter are shown. 
The animal life of the period is characterized by the abund- 
ance of Crinoids or sea-lilies. These reached their greatest de- 
velopment at this time. Such genera as Platycrinus, Batocrinus , 
Actinocrinus , Agaricocrinus, etc. , are represented by many species. 
Those specimens having the arms and stems attached are of par- 
ticular interest. 
Pentremites, Cryptoblastus, Schizohlatsus, Granotocrinus, etc., 
are typical Blastoids, or bud-like animals, and are near rela- 
tives of the Crinoids. 
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, Euompholus, Belter ophon, 
Pleurotomaria, Naticopsis, etc., are still abundant. 
The plain-sutured Nautilus and the zigzag-sutured Gonia- 
tites are the principal Cephalopods. 
The Trilobites have disappeared and in their place is shown 
Euprops which somewhat resembles the Horseshoe crab. 
The size of Carboniferous fish is indicated by the teeth of 
Rhizodus, the scales of Megalichthys, and the spines of Ctena- 
canthus. 
Permian, or Closing Period of the Paleozoic Era. — Fishes are 
represented by Paleoniscus, joatrachians by Archegosaurus, an 
animal which combined the characters of Batrachian and fish. 
It had both lungs and gills, and was covered with scales. Plants 
are represented by leaves of Walchia, a Ly copod, and Alethopteris 
one of the Ferns. 
The invertebrate fossils of the period shown are mostly 
Brachiopods and Pelecypods. They do not differ in any marked 
