UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 9, No. 15, pp. 261-360, pis. 12-35 Issued May 1, 1916 



MESOZOIC AND CENOZOIC MACTRINAE 



I 



OF THE PACIFIC COAST OF NORTH AMERICA 



BY 



EARL L. PACKARD 



CONTENTS 



Page 



Introduction 262 



Historical Sketch 263 



Basis of Classification 265 



Variations of the Elements of the Mactrine Shell 267 



History of the Mactrinae 273 



The Geologic and Geographic Range of the Pacific Coast Mactrinae — 



facing 274 



Phylogeny of the Pacific Coast Mactrinae 276 



Conclusions 277 



Systematic Description "of the Mactrine Species 277 



Superfamily Mactracea Gray 277 



Family Mactridae Gray '. 277 



Subfamily Mactrinae Dall 278 



Genus Mactra Linnaeus 278 



Subgenus Mactrotoma Dall 278 



Section Mactrotoma Dall 278 



Mactra nasuta Gould 278 



Section Simomactra Dall 279 



Mactra dolabriformis (Conrad) 279 



Section Micromactra Dall 279 



Mactra californica Conrad 280 



Subgenus Mactrella Gray 281 



Mactra exoleta Gray 281 



Mactra trampasensis, n. sp 282 



Genus Spisula Gray 283 



Subgenus Hemimactra Swainson 283 



Section Mactromeris Dall 283 



Spisula voyi (Gabb) 283 



Spisula catilliformis Conrad 285 



Spisula mercedensis, n. sp 286 



