CONTENTS. XV 
CHAPTER IV. 
PAGE 
The Elfin-fish of Gawin Douglas. — The Fish of the Old Red 
Sandstone scarcely less curious. — Place which they occu- 
pied indicated in the present Creation by a mere Gap. — Fish 
divided into two great Series, the Osseous and Cartilagi- 
nous. — Their distinctive Peculiarities. — Geological Ilustra- 
tion of Dr. Johnson’s shrewd Objection to the Theory of 
Soame Jenyns. — Proofs of the intermediate Character of the 
Ichthyolites of the Old Red Sandstone. — Appearances which 
first led the Writer to deem it intermediate. — Confirmation 
by Agassiz. — The Osteolepis.— Order to which this Ichthy- 
olite belonged. — Description. — Dipterus. — Diplopterus. — 
Cheirolepis. — Glyptolepis, : , ; : - ‘ 55-78 
CHAPTER V. 
The Classifying Principle and its Uses. — Three Groups of Ich- 
thyolites among the Organisms of the Lower Old Red Sand- 
stone. — Peculiarities of the Third Group. — Its Varieties. — 
Description of the Cheiracanthus. — Of two unnamed Fossils 
of the same Order. — Microscopic Beauty of these ancient 
Fish. — Various Styles of Ornament which obtain among 
them. — The Molluses of the Formation. — Remarkable chief- 
ly for the Union of modern with ancient Forms which they 
exhibit. — Its Vegetables. — Importance and Interest of the 
Record which it furnishes, : ; ‘ , , 4 79-94 
CHAPTER Y¥Ff. 
The Lines of the Geographer rarely right Lines. — These last, 
