119 



pie, varying in this respect; more reflected and aperture more 

 effuse at the columella. Parietal wall in the heavier examples 

 calloused, the callous connecting with the inner edges of the outer 

 lip above and below. Shell rather fragile, thin, translucent, sur- 

 face smooth and shiny, and sculptured with fine incremental lines, 

 color pale horn to white, and otherwise marked by a single narrow 

 revolving reddish-brown band just above the periphery, which in 

 some specimens is obscure or absent. In some individuals certain 

 faint scars upon the upper whorls imply an occasionally hirsute 

 character. Max. diam. of largest 15.25, of smallest adult 13.75; 

 Min. diam. of largest 13.25, of smallest 12, Alt. of largest 10.25, 

 of smallest adult 8.75 mm." — Stearns, U. S. Natl mus pr 13:206, 

 t 15, f 6-8. 



Type locality: — Grand canyon of the Colorado, opposite Kai- 

 bab plateau, at an elevation of 3,500 feet (C. H. Merriam). 



Stearns, Nautilus 8:29 records from Resting Springs, Inyo 

 Co., Cal. (Vernon Bailey), and Mountain Springs, San Diego Co., 

 Cal. (C. R. Orcutt). 



1635 Mactra (Mactroderma) velota Phil. 1848. 

 Gulf of Cal. to Panama. 



1636 Mactra (Mactrotoma) nasuta Gld. 1851. 

 Baja Cal. to west Columbia. 



Synonymy: M. californica Desh. (not Conr.). — M. hiantina 

 Desh. etc. 



1637 Mactra (Mactrella) exoleta Gray, 1837. 

 Gulf of Cal. to Guayaguil. 



1638 Mactra (Mactrella) elegans Sby. 1825. 

 Gulf of Cal. to Panama. 



1639 Spisula (Hemimactra) catilliformis Conr. 18 67. 

 Neeah bay, Wash., to San Diego, Cal. 



Synonymy: Standella californica Cpr. not Conr. — Mactra ca- 

 tilliformis Dall. 



1640 Spisula (Hemimactra) Hemphilli Dall. 1894. 

 San Diego, Cal. 



1641 Spisula (Hemimactra) plamilata Conr. 1837. 

 Monterey to San Diego, Cal. 



1642 Spisula (Hemimactra) polymyma Stm. 1860. 



1643 Variety alaskana Dall. 1894." 

 Icy Cape to Neeah bay, Wash. 



1644 Muiinia palida Brod. & Sby. 1829. 

 Cape San Lucas to Panama. 



1645 Muiinia Gabbi Tryon. 1869. 



Lower California. Near M. exalbida Gray, of South America 

 (Dall). 



1646 Gnathodon (Rangianella) mendicus Gld. 1851. 

 Estuaries, Gulf of California. 



1647 Labiosa anatina Spengler. 1802. West Mexico. 



1648 Tresus Nuttallii Conr. 1837. 

 Sitka, Alaska to San Diego, Cal. 



Synonymy: Lutraria maxima Midd. 1849, non Jonas 1844 — 

 L. capax Gld. 1850. — L. inflata Dunker, 1853. 



