NO. 1545. NEW FOSSIL MOLL USKS FROM CALIFORNLi— ARNOLD. 539 



angles flat or slightly concave and ornamented by four (including those 

 at the angles) prominent spiral ridges; l)oth above the upper angle 

 and below the lower one is a similar ridge; suture quite deeply im- 

 pressed; base practically flat, faintly spirally sculptured; aperture 

 subquadrate. 



Dlnienstons. — Of the type, an imperfect specimen, altitude, 31 mm.; 

 latitude, 12 mm.; altitude of body whorl, 13 mm. 



Notef<. — The spiral ribs in this variety are all of about equal prom- 

 inence while in the typical Pleistocene forms the rib on each angle is 

 much more prominent than those between, the latter being little more 

 than raised lines; the surface of the whorl between the angles is also 

 less concave and the general shape of the shell less slender in var. ftv- 

 7iandoensU than in typical cooper!. 



Type.— C^it. No. 164957, U. S. N. M. 



Locality. — Elsmere Canyon, near the Pacitic Coast Oil Company's 

 wells, 2^ miles southeast of Newhall, Los Angeles County, California. 

 (Ralph Arnold.) 



Horizon. — Middle Fernando formation (Lower Pliocene). 



EXPLANATION OF PLATE8. 



All figures are natural size unless otherwise indicated. Unless otherwise indicated 

 all specimens figured are from California. 



Plate XXXVIII. 



Fig. 1. Venerimrdia planicosta Lamarck. Cat. No. 164973, LT.8.N.M. Left valve; 

 longitude, 84 mm. Eocene, Little Falls, Washington. This isthe most wide- 

 spread and characteristic Eocene species in the world. Found in the Sespe 

 and Silver Thread districts, Ventura County. 

 la. View of anterior end of both valves of same. 

 lb. View from above of both valves of same. 



2. Cardiwn cooperii Gabb. Cat. No. 164998, U.S.N.M. A decorticated right 



valve; longitude, 35 mm. Eocene, Rose Canyon, San Diego County. A 

 common species in the Eocene of the West Coast. 

 2a. View of both valves of same specimen from above. 



3. Meretrix hornil Gabb. Left valve; longitude, 36 mm. Pal. Cal., II, pi. xxx, 



fig. 78. A common species in the Eocene of the west coast. 



4. Modiolus ornatus Gabb. Right valve; longitude, 38 mm. Pal. Cal., I, pi. 



XXIV, fig. 166. Another species found in most Eocene faunas of the West 

 Coast. 



Figures 3, '^a, 'db, 5. and 7 are copied from Pal. Cal., I and II. 



Fig. 1. Pectf.ii {Chlami/s) calk'msl Arnold. Collection Lniv. California. An imper- 

 fect left valve; altitude 45 mm. Eocene, Sisar Creek, Ventura County. 



2. Same species as fig. 1. Imperfect right valve; altitude, 29 mm. Same locality 



and collection as fig. 1. 



3. Pectcn (Propeamusmm) inierradlaius Gabb. Left valve; altitude, 25 nnn. 



Eocene shales at New Idria, San Benito County, and in Silver Thread 

 district, Ventura County. 



