CLASS GASTROPODA 
129 
outer lip thin, showing the external sculpture within; inner lip almost 
straight and slightly revolute; parietal wall covered with a thin callus. 
Length, 6.1; diameter, 1.9 mm. (Bartsch.) 
Type in United States National Museum, No. 250625. Type locality, 
San Diego Bay, California. 
Range. Known only from type locality. 
Turbonilla ista Bartsch, 1917 
Proceedings of the United States National Museum, 52:650; PI. 42, fig. 6. 
Shell rather large, elongate-conic, light brown. Early whorls light 
yellow. Nuclear whorls decollated. Post-nuclear whorls appressed at 
the summit, which is slightly excurved, marked by rather poorly de¬ 
veloped, almost vertical, axial ribs, which become obsolete on the later 
whorls. Of these ribs, eighteen occur upon the second and third, twenty 
upon the fourth, twenty-two upon the fifth, twenty-four upon the sixth, 
twenty-six upon the seventh, twenty-eight upon the eighth, thirty upon the 
ninth, and thirty-two upon the tenth, while upon the penultimate they are 
too irregular to be counted. Intercostal spaces very feebly impressed, 
about as wide as the ribs. The spiral sculpture consists of strong and 
weak incised lines, the strong lines pass strongly upon the sides of the 
ribs and even cross the summit; the first of these strong lines is about 
one-fifth of the distance between the summit and the suture anterior 
to the summit, while the spaces between the first and second, the third 
and fourth, the fourth and fifth, and the fifth and sixth are almost equal 
and about two-thirds as wide as that between the second and third; of 
the finely incised spiral lines eight occur between the first and second, 
the anterior member of these being much stronger than the other two; 
there are also three between the second and third, the last two of these 
being closer spaced than the first two; no fine lines are apparent between 
the other strong lines. Sutures slightly constricted. Periphery of the last 
whorl strongly inflated. Base short, well-rounded, marked by the feeble 
continuations of the axial ribs and twenty-two wavy incised lines, which 
are of varying width and spacing. Aperture moderately large, subquadrate, 
posterior angle obtuse; outer lip thin, showing the external sculpture 
within; inner lip oblique, straight, slightly revolute; parietal wall glazed 
with a moderately thick callus. Length, 12.5 ; diameter, 2.8 mm. (Bartsch.) 
Type in United States National Museum, No. 250627. Type locality, 
off San Diego Bay, California. 
Range. Known only from type locality. 
[427 ] 
