vm CONTENTS. 



V. 



CATALOGUE OF SHELLS, WITH DESCRIPTIONS OF NEW SPECIES. 

 BT DB. A. A. GOULD. 



Catalogue 243-245 



VI. 



PISHES 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 vaiious parts of the 

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

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

 carbonarius, Agass., 271-6. — A. rynchaus, Agass., 276-7. — A. Rupertianus, 

 277-8. — On the position of the Siluridse and Goniodonts as aberrant 

 families of the order of Gadoids, 278-9. — The genus Pimelodus ; proba- 

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

 P. felts, Agass., 281-4. — Genus Percopsis, Agass., representative of an 

 ancient type of the tertiary period ; intermediate between Percoids and 

 Salmonidse, 284-5. — P. gutiatm, Agass., 286-9. — Percoids ; great dif- 

 ference in their distribution, between Lake Superior and the Lower 

 Lakes, 289-91. — Observations on Perca flavescens, 291-3. — On Potnotis 

 vulf/aris, 293. — Lucioperca Americana; value of the opercular spines as 

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

 Huro nigricans, 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; P^cilosoma, Agass., Boleosoma, 298-9. — Cot- 

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

 300. — C. Richanhoni, Agass.. 300-3.— C. FranJdini, Agass., 303-4.— 

 BoLEOsoMA, characters of, 304. — B. mactilatum, Agass., 305-7. — Pileoma; 

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

 ncbulosus, Agass., 310-14. — G. pygm(eus, Agass., 314-15. — Family 

 EsociD^, 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. 



