264 University of California Publications in Geology [Vol. 9 



The first mactrine species reported from the Pacific Coast region 

 of North America was Mactra calif or nica*, described by Conrad in 

 1837 from Santa Barbara, California. Other species were subse- 

 quently described by the same author in various papers, the last of 

 which appeared in 1867 ; his list of species is completed by the fol- 

 lowing : Mactra albaria, M. catilliformis, M. diegoana, M. planulata, 

 Mactra (?) gabiotensis, Mulinia densata and Spisula dolabriformis. 

 Conrad 5 also contributed in 1867 a synopsis of the Mactridae in 

 which he designated a typical species for each of his taxonomic 

 groups. Gray in the latter part of 1837 defined the superfamily 

 Maetraeea, the family Mactridae and several genera as now recog- 

 nized. Among his new species a West Coast form appears under 

 the name of Mactra exoleta. 



During 1848-50 Gould described Mactra falcata and M. nasuta, 

 and Meek reported in 1861 the new species, M. gibbsana, which he 

 obtained in a boulder of doubtful Cretaceous age, from the Straits 

 of Juan de Fuca. Remand described a Mulinia in 1863 under the 

 name Cardium gabbii, which later became the type of Gabb's genus 

 Pseudocardiuin. 



Gabb described in 1869 the genus Cymbophora, the typical species 

 of which he had previously named Mactra ashburnerii. His new 

 mactrine species include : Callista voyi, Hemimactra lenticnlaris, 

 Hemimactra (?) occidentalis, Lutraria truncata, Mactra ashburnerii, 

 Mactra (?) tenuissima and Schizodesma abscissa. 



The eastern species Mactra warrenana Meek was reported by 

 Whiteaves from the Cretaceous of the San Juan Islands, Washing- 

 ton, but later it was referred by the same author to one of Gabb's 

 West Coast forms. 



Dr. W. H. Dall made the next contribution to the knowledge 

 of the West Coast Mactridae, when in 1894 he published a synopsis 

 of both the East and West Coast species". This was amplified during 

 the following year 7 , and again later in the Transactions of the 



4 References to the original descriptions of the species mentioned in this 

 section may be found under the headings of the species in question in the 

 systematic portion of this paper. 



s Conrad, T. A., Catalogue of the Family Mactridae, Amer. Jour. Conch., 

 vol. 3, appendix, pp. 30-47, 1868. 



s Dall, W. H., Synopsis of the Mactridae of northwest America, south to 

 Panama, Nautilus, vol. 8, pp. 25-28, and pp. 39-43, 1894. 



i Dall, W. H., Synopsis of a review of the genera of Recent and Tertiary 

 Mactridae and Mesodesmatidae, Proc. Mai. Soc. London, vol. 1, pp. 203-213, 

 1895. 



