18 FIELD MUSEUM OF NATURAL HIST ORY 
Cordaites appears to be allied to both the Conifers and the 
Cycads. It had a straight trunk 60 or 70 feet in height and long 
narrow leaves. Trigonocarpum and Cardiocarpum are supposed 
to be the fruit of this tree. 
Calamites, Annularia, etc., are allied to the Equisetum or 
modern Horsetails. Stems of the former and leaf whorls of the 
latter are shown. 
A portion of a trunk of a tree of this period is shown in a 
floor case. This trunk is about two feet in diameter and the 
portion shown is six feet in height. On the wall an oil painting 
represents a forest of this age, with Ferns, Club-mosses, Equi- 
setcC, etc., grown to the height of forest trees of the present day. 
The size of fish of the period is indicated by the teeth of 
Rhisodus, the scales of Megalichthys, and the spines of Ctena- 
canthus, 
Permian, or Closing Period of the Paleozoic Era. Fishes of 
this period are represented by Paleoniscus, and batrachians by 
Archegosaurus, an animal which combined the characters of 
batrachian and fish. It had both lungs and gills, and was cov- 
ered with scales. Plants are represented by leaves of Walchia, 
a Lycopod, and Alethopteris, one of the Ferns. 
The invertebrate fossils of the period shown are mostly 
Brachiopods and Pelecypods. 
Triassic Period.— This period is the first of the Mesozoic era 
or Age of Reptiles. The land plants of the period are illustrated 
by series of impressions of the leaves of Pterophyllum, a Cycad, 
and stems of Equisetum, a form allied to the modern Horsetails. 
Sponges are represented by Stellispongia and Corynella. Cri- 
noids by Encrinus, and Sea-urchins by detached spines of 
Cidaris. 
Molluscs of this period assumed a decidedly modern appear- 
ance. This is illustrated by Lima, Pleuromya, Nucula, Myo- 
phoria and Modiola of the Pelecypods and Monodonta, Holo- 
pella, and Murchisonia of the Gastropods. Two new types of 
Cephalopods are shown. Ceratites has serrated suture lines 
and Arcestes and Rhacophy Hites are true Ammonites having 
complex lobed sutures. 
Pemphix is a crustacean of the type of the modern lobster. 
Triassic fish are illustrated by the teeth of Ceratodus and 
nearly complete specimens of Ischypterus and Samionotus. 
