Vlii CONTENTS. 



V. 



CATALOGUE OF SHELLS, WITH DESCRIPTIONS OF NEW SPECIES. 

 BY DR. A. A. GOULD. 



Catalogue 243-245 



* 



VI. 



FISHES OF LAKE SUPERIOR COMPARED WITH THOSE OF THE OTHER GREAT CANADIAN 



LAKES. 



Geographical distribution ; the prevalence of general laws over 

 mere peculiarities of position and circumstances, 246-7. Migrating 

 animals do not wander, but regularly return ; light thrown on the 

 question of unity or plurality of creations by the examination of the 

 fishes of Lake Superior, 248. Examination of the question whether 

 the Petromyzons should form a subclass by themselves, or be classed 

 with the skates and sharks, and conclusion that they are simply embry- 

 onic forms of the latter type, 249-52. Description of Ammoccetes 

 borealis, 252-4. LEPIDOSTEUS, as showing the reptilian character of the 

 ancient fishes, 254-63. The sturgeons ; their geographical distribution, 

 263-4. Circumscribed within narrow limits in various parts of the 

 world, yet linked together by intermediate forms ; peculiarity of their 

 distribution in America, 265-6 Acipenser Itevis, Agass., 267-71. A. 

 carbonarms, Agass., 271-6. A. ryncha>ns, Agass., 276-7 A. Rupertianus, 

 277_8. On the position of the Siluridai and Goniodonts as aberrant 

 families of the order of Ganoids, 278-9. The genus PIMELODUS ; proba- 

 bly to be further subdivided ; remarks on several species, 279-80. 

 P.felis, Agass., 281-4. Genus PEHCOPSIS, Agass., representative of an 

 ancient type of the tertiary period ; intermediate between Percoids and 

 Salmonida;, 284-5. P. guttatiis, Agass., 286-9. PERCOIDS ; great dif- 

 ference in their distribution, between Lake Superior and the Lower 



Lakes, 289-91 Observations on Perca Jlavescens, 291-3. On Pomotis 



rulifaris, 293. Lucioperca Americana; value of the opercular spines as 

 distinctive mark in this genus, 294-5. Grystes fasciatus, Agass., 295-7. 

 Hum nitiricans, Cuv., a Grystes, 297. COTTOIDS ; importance of correct 

 appreciation of the connecting character, rather than the amount of 

 external variation, in classification, 297-8 Subfamily of ETHEOSTOMATA ; 

 ETHEOSTOMA ; PILEOMA ; PJLCILOSOMA, Agass., BOLEOSOMA, 298-9. COT- 

 TUS ; character of genus ; various opinions as to number of species, 

 300. C. Richardsoni, Agass.. 300-3. C. Franklini, Agass., 303-4. 

 BOLEOSOMA, characters of, 304. B. maculatum, Agass., 305-7. PILEOMA; 

 characters of this genus, 307-8. P. zebra, Agass., 308-10. Gasterosteus 

 nebulosus, Agass., 310-14. G. pi/gmmis, Agass., 314-15. Family 

 ESOCID^E, 315-17 Esox boreus, Agass., 317-21. Family GADOIDS ; ob- 

 scurity of their real affinities ; disagreements and uncertainties as to 

 certain North American genera and species, 321-4. Lota maculosa, 



