CLASS GASTROPODA 
119 
flattened in the middle, rounding moderately toward the summit and the 
periphery, marked by strong, regular, retractive, axial ribs, of which 
fourteen occur upon the second of the remaining turns, sixteen upon the 
third, eighteen upon the fourth to sixth, twenty upon the seventh and 
eighth, while upon the remaining volutions they become much enfeebled 
and less regular. These ribs upon the middle whorls are strongest in 
the middle, sloping gently toward the summit and periphery, the slope 
at the summit lending them a shouldered effect. Intercostal spaces 
deeply impressed, about as wide as the ribs. Sutures strongly im¬ 
pressed. Periphery of the last whorl somewhat inflated, well-rounded. 
Base moderately long, well-rounded, marked by the feeble continuations 
of the axial ribs. Entire surface of spire and base crossed by numerous 
very fine, spiral striations. Aperture subquadrate; posterior angle obtuse; 
outer lip, showing the banding of the exterior within; inner lip very 
oblique, slightly curved, and revolute, with an obscure fold at its in¬ 
sertion ; parietal wall glazed with a very thin callus. Length, 8.3; diam¬ 
eter, 2 mm. (Bartsch.) 
Type in United States National Museum, No. 211511. Type locality, 
outside San Diego, California. 
Range. Known only from type locality. 
Turbonilla pesa Dali and Bartsch, 1910 
Canada, Department of Mines, Geological Survey Branch, Memoir No. 14-N, 14; 
PI. 2, fig. 5. 
Shell elongate-conic, small, chestnut-brown, with a slightly paler, 
broad, obscure band half way between the sutures. Nuclear whorls decol¬ 
lated. Post-nuclear whorls flattened, slightly shouldered at the summit, 
marked by feeble, almost vertical, axial ribs; of which twenty-two occur 
upon the second, twenty-four upon the third, twenty upon the fourth 
and fifth, and twenty-six upon the sixth of the remaining turns. Upon 
the penultimate turn the ribs are subobsolete. Intercostal spaces feebly 
impressed, of irregular width. Sutures well-impressed. Periphery of 
the last turn somewhat inflated, well-rounded; base short, well-rounded. 
Entire surface of spire and base crossed by numerous very fine, closely 
spaced, spiral striations. 
Aperture broadly oval; posterior angle acute; outer lip thin, showing 
the external markings within by transmitted light; columella moderately 
strong, slightly curved, and revolute. Length, 6; diameter, 1.6 mm. (Dali 
and Bartsch.) 
Type in ? Type locality, Barkley Sound, Vancouver Island, British 
Columbia. 
Range. Known only from type locality. 
[417] 
