194 University of California Publications in Geology [Vol. 8 



This species is nearer to Drillia johnsoni Arnold, than to any other 

 species reported from California. It may be distinguished from the 

 latter by the lack of spiral sculpture, less pronounced sutural band, 

 and the width of the interspaces ; those in Drillia johnsoni Arnold 

 are wider than the ribs while in this species they are equal to the ribs. 



DRILLIA MERCEDENSIS, n. sp. 

 Plate 22, figures 2a, 2b, and 2c 



Shell small, fusiform, with seven or eight sculptured whorls; spire 

 high, one-third total length of the shell; apex acute; whorls of the 

 spire broadly convex, sculptured with three narrow threadlike grooves 

 and about twenty-one obscure axial riblets, spiral grooves near the 

 suture more pronounced than the one intervening, and producing two 

 sutural bands, one on the posterior and one on the anterior margin 

 of each whorl ; spaces between the grooves faintly nodose spiral bands 

 of unequal width, the second from the posterior margin much the 

 broadest and occurs at the widest portion of the whorl ; anterior spiral 

 band partly obscured by the succeeding whorl; the axial ribs follow 

 the lines of growth and are sharply curved near the central part of 

 each whorl ; they are most pronounced on the posterior and frequently 

 absent from the anterior portion of the whorls ; suture distinct, im- 

 pressed ; body-whorl ornamented with about twenty nodose axial rib- 

 lets and ten to twelve spiral bands which are separated by narrower 

 grooves ; axial ribs follow the lines of growth and are most pronounced 

 in front of the suture, becoming obsolete on the anterior portion ; 

 spiral bands faintly nodose where crossed by the axial riblets, they 

 are broadest on the middle of the whorl, becoming narrower and equal 

 in width to the grooves on the anterior portion; aperture elliptical; 

 outer lip thin, arcuate; inner lip and columella slightly incrusted; 

 columella recurved; posterior sinus broad and shallow; canal mod- 

 erately short, curved. 



Dimensions. — Altitude of the type, 22.5 mm. ; maximum diameter 

 of the shell, 9 mm. ; length of the aperture, 8 mm. ; length of the canal, 

 3 mm. 



Occurrence. — The type and several other specimens were obtained 

 from the Merced Series near Santa Rosa. A large number of speci- 

 mens were also obtained from the Merced Series south of San Fran- 

 cisco and at Bolinas Bay. 



