288 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
forms a continuous pitted element. Periphery of the last whorl well- 
rounded, marked by a narrow, deeply incised channel which is also crossed 
by fine axial threads that render it pitted. Base well-rounded, marked by 
13 spiral cords, of which the anterior 3 are very feeble, while the rest 
are very regular in size and spacing, becoming successively a little more 
slender from the periphery anteriorly. The spaces that separate these cords 
are almost as wide as the cords and are marked by slender axial threads 
which give to the spiral grooves a strongly pitted appearance. Aperture 
large; posterior angle obtuse; somewhat channeled at the junction of the 
columella and basal wall and decidedly flaring at the junction of the outer 
lip and basal lip; outer lip thin, showing the external sculpture within by 
the transmitted light, sinuous at the edge; columella very stout, rather 
evenly curved, provided with an oblique fold a little anterior to its inser¬ 
tion ; parietal wall glazed with a thin callus. 
Type in United States National Museum, No. 362447. Type locality, 
San Clemente Island, California. It has a little more than four post- 
nuclear whorls, having lost the nuclear turns, and measures, length, 
3.2 mm.; diameter, 1.9 mm. 
Odostomia chacei Bartsch, 1927 
Proceedings of the United States National Museum, 70: 16; PI. 3, fig. 3. 
Shell elongate-ovate, bluish white. Nuclear whorls two and one-half, 
well-rounded, forming a depressed helicoid spire which is about one-half 
obliquely immersed in the first of the succeeding turns. The tilted edge of 
the last volution shows four rather strong spiral cords. Postnuclear whorls 
stout, separated by a profoundly channeled suture, marked by exceedingly 
strong axial ribs which on all but the last whorls are slightly protractive; 
on the latter they are almost vertical. Of these ribs 16 occur upon the 
second and third and 18 upon the penultimate turn. The intercostal spaces 
are about as wide as the ribs. In addition to the axial sculpture the whorls 
are marked by four strong spiral cords which render their junction with 
the axial ribs strongly tuberculated. The tubercles are almost hemispheri¬ 
cal, sloping only very slightly, a little more abruptly posteriorly than an¬ 
teriorly. The spaces inclosed between the axial ribs and the spiral cords 
are well-rounded profound pits. The summit of the whorls is tabulated. 
The summits of the strong ribs render the suture slightly sinuate. Periph¬ 
ery of the last whorl marked by a rather strong spiral cord. Base mode¬ 
rately long, well-rounded, marked by five spiral cords which become 
slightly closer spaced from the peripheral cord anteriorly and also decid¬ 
edly progressively enfeebled in the same direction. The broad spaces that 
separate the spiral cords are marked by numerous slender axial threads. 
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