252 University of California Publications in Geology [Vol. 8 



AGASOMA BARKERIANUM Cooper 



Plate 25, figures 3, 13, and 14 



Conrad, Pac. R. R. Repts., vol. 5, pi. 7, figs. 63, 68, 1856. 

 ? Natica geniculate! Conrad, Pac. R. R. Repts., vol. 5, p. 328, pi. 7, fig. 67, 

 1856. 



Agasoma barkerianum Cooper, Bull. 4, Calif. Min. Bureau, p. 53, pi. 5, 

 fig. 63, 1894. 



Shell rather thin, shape roughly bi-conieal ; spire low, apical angle 

 70° to 75° ; whorls five to six ; prominent flaring carina on last one 

 or two whorls; carina bounded above by impressed suture, while for 

 a short distance below carina the body-whorl is concave in outline; 

 shell marked by fine spiral lines generally alternating in width, two or 

 three lines to the millimeter ; these crossed by irregular faint lines of 

 growth; growth lines replaced by ribs on early whorls, giving them 

 a cancellated appearance ; on some specimens from one to five of the 

 spiral lines on body-whorl are heavier than the rest and along them 

 is distributed a series of irregularly spaced, horizontally elongated 

 tubercles ; callus thick, especially on large specimens, extends above 

 the suture on the last two whorls; mouth-opening lenticular; canal 

 slightly curved, short, wide. Immature specimens are thinner, callus 

 less prominent, and the fine growth lines are replaced by vertical ribs. 



Height 55 mm., width 32 mm.; mouth-opening length 40 mm., 

 width 15 mm. ; maximum height 63 mm. 



This species is characteristic of the Temblor (Monterey?) for- 

 mation; Barker's Ranch. Kern County (Cooper; F. M. Anderson "> : 

 San Luis Obispo County (Cal. Acad. Sci. Coll.) ; ? Puente formation, 

 Raymond Hill. Los Angeles County (Arnold). 



AGASOMA BARKER! A NUM Cooper, var. SA N T ACRTJZ ANUM Arnold 



Plate 25, figures 11 and 12 



Agasoma santacruzana Arnold, Proo. IT. S. Nat. Mus. vol. 34, p. 379, pi. 34, 

 fig. 7, 1908. 



Agasoma santacruzana Arnold, U. S. Geol. Survey Bull. 396, p. 18, pi. 8, 

 fig. 5, 1909. 



Arnold states that this form differs from the typical A. barkerianum 

 "in having a lower spire, a broader but less sharply nodose carina 

 on the body-whorl, and in lacking the prominent nodose angles on 

 the middle of the body-whorl." These are all variable characteristics, 

 and a gradation from the typical A. barkerianum to the santacruzanum 

 form is fonnd in a series of specimens from a single locality in the 



