III. COTTOIDS OF NORTH AMERICA. 79 



CONTENTS. 



PAGE 



PREFACE ........... 3 



CHAPTER I. 



ON THE FRESH WATER COTTOIDS IN GENERAL. 



1. Zoological considerations ......... 5 



2. Genealogy of the Cottoids ......... 10 



3. Geographical distribution ......... 11 



4. Habits, food, and use ......... 12 



CHAPTER II. 



ANATOMICAL OBSERVATIONS. 



1. General remarks .......... 14 



2. The bony frame of Coitus viscosus ........ 14 



3. Comparisons between the skulls of different Cotti ...... 19 



4. Comparative osteology of C. viscosus and A. virginianus . . , . .20 



5. The bony frame of Triijlopsis Thompsonii . . . . . . .21 



6. Triglopsis Thompsonii compared with Coitus viscosus and with Acanthocot/us virginianus . 25 

 7. The encephala of Cottus viscosus, C. gracilis, C. gobioides, Trujlopsis Tlwinpsonii, Acantlio- 



cottus virginianus, and A. variabilis, compared . . . . .26 



8. The muscular system of Coitus viscosus ....... 28 



9. The skin and the lateral line in Cottoids ....... 30 



10. The alimentary canal, urinary bladder and ovaries, in Cottoids . . . .31 



11. Respiratory apparatus ......... 32 



CHAPTER III. 



ON THE GENUS COTTUS, Artedi. 



1. Zoological characters ......... 33 



Synoptical table of the species ....... 36 



2. Chronological summary of the history of American Cotti . . . . .37 



3. Species with four soft rays to the ventrals ....... 39 



I. Cottus Richardsonii ........ 39 



II. Cottus cognatus ........ 41 



III. Cottus Wilsonii . . . .42 



IV. Cottus Bairdii ........ 44 



V. Cottus Alvordii ........ 46 



VI. Cottus meridionalis . . 47 



