490 University of California Publications in Geology I Vol. 9 



this whorl. The junctions of the spiral cords form rounder tubercles 

 and spaces between appear to be round. The fifth, sixth, seventh and 

 eighth whorls are decorated by four spiral cords, the first of which is 

 slightly anterior to the summit ; the second equal in size to first, and 

 separated from it by an interspace equal in width to the first cord. 

 These two cords occupy about the upper two-fifths of the whorl, while 

 the two lower and much stronger cords cover the rest of the whorl. 

 Vertical axial ribs slightly weaker than the spiral cords also mark 

 these whorls. The nodes made by the crossing of the two sets of 

 lines are elongated from left to right. This is most marked in the 

 two posterior ribs. In addition to these decorations swollen varices 

 occur upon the whorls at irregular intervals. These varices are very 

 strongly marked by the spiral cords, the axial ribs being very weak. 

 Of the axial ribs fifteen occur upon the fifth, sixteen upon the sixth, 

 twenty upon the seventh and eighth. The ninth, or body-whorl, is 

 similarly decorated. Its base is marked by two strong spiral keels, 

 the first of which is nodose, and by six or seven spiral lines. Aperture 

 roughly oval ; columella twisted and covered by a thin callus. 



This species is much smaller than either C. excelsa Dall or C. alter- 

 nata Gabb. Its well-marked varices and the lesser number of spiral 

 cords distinguish it at once from C. excelsa. It is broadly conic while 

 C. alternata is elongate conic. C. orovillensis n. sp. has two sets of 

 spiral cords, an upper and weaker and a lower and stronger, while the 

 weaker and stronger cords of C. alternata, as the name suggests, 

 alternate. 



Dimensions. — Length, 6 mm. ; diameter, 2 mm. 

 Occurrence. — University of California Locality 2225, south side of 

 Oroville South Table Mountain. 



DRILLIA OROVILLENSIS, n. sp. 

 Plate 41, figure 4 



Shell slender, fusiform, with spire acutely pointed ; whorls eight, 

 of which two nuclear are smooth ; last whorl three-fifths of the length 

 of the shell. The transverse sculpture consists of twelve sharply 

 elevated flexuous ribs with interspaces twice their width and fine 

 threads parallel to ribs in the interspaces. These ribs are largest at the 

 shoulder, which is located at the middle of a spire-whorl. Five spiral 

 lines cross the ribs and one larger than the rest is found at the angle. 

 The flexuous transverse ribs on the body-whorl extend from the linear 



