(X<::_.*^-^^ NATURAL SCIENCES OF PHILADELPHIA. 463 



DESCRIPTIONS OF NEW FOSSIL SHELLS FROM THE TERTIARY OF 

 CALIFORNIA. 



BY ROBERT E. C. STEARNS, UNIVERSITY OF CALIFORNIA. 



SCALARIA LoAuarck. 



Subgenus Opalia, H. & A. Ad. 

 Opalia varicostata, Steams. Plate 27, Figs. 2-5. 



Shell elongated-conical, turreted, tapering, solid, imperforate, 

 aperture ovate, peristome continuous, thickened ; dingy to clear 

 white ; suture well defined ; whorls united, exceedingly variable 

 in convexity and altitude ; specimens all decollate, or truncated, 

 equally solid, though varying in length from .75 to 2.45 inches, 

 showing four and one-half whorls within the first measurement 

 to five in the latter. Perfect specimens have probably from 8 to 

 12 whorls, or even more. Longitudinal ribs 9 to 12, varying in 

 number, prominence, and regularity, as well as in obliquity', when 

 compared with the axial line of the shell, and, in some specimens, 

 irregularly thickened and distorted by the intrusion of a varical 

 rib more or less conspicuously. In some individuals the termi- 

 nation of the rib at the suture gives the upper part of the whorls 

 a crenulated appearance, and the suture in all specimens is more 

 or less waved, dependent upon the prominence of the ribs, which 

 terminate anteriority at and join a transverse rib at about the 

 middle of the basal whorl. 



Number of specimens 22, all in good condition, save the erosion 

 of the apex. 



This is one of those plastic forms which exhibit great varia- 

 bility, but which when a sufficient number of specimens are com- 

 pared, show well-marked characteristics. 



Had the twenty-two specimens examined as above been collected 

 b}' several persons, and, therefore, divided into many and smaller 

 parcels, and sent, as quite likely would have been the case, to 

 different authors and museums, and thus too widely separated for 

 comparison, it is highly probalile, when the latitude of variation 

 which this form presents is considered, that three or four species 

 would have been made out of the above material, which Mr. 

 Henry Hemphill, the collector, kindly placed in my hands for 

 determination. 



