172 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type in United States National Museum, No. 196297. Type locality, 
off Del Monte, Monterey Bay, California, in 12 fathoms. 
Range. Known only from type locality. 
Odostomia pedroana Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 172; PI. 19, figs. 8, 8a. 
Shell large, robust, chocolate-brown. Nuclear whorls two, moderately 
large, forming a helicoid spire whose axis is at right angles to that of the 
succeeding turns, in the first of which it is about one-fifth immersed. 
Post-nuclear whorls very strongly sculptured, with three spiral keels 
between the sutures, one of which at the summit is slender, the other two 
are strong and equal, the supraperipheral one being about as far posterior 
to the suture as the one at the summit is from its neighbor. In addition 
to the spiral keels the whorls are marked by narrow retractive axial ribs, 
of which fourteen occur upon the first, sixteen upon the second to third, 
eighteen upon the fourth, twenty upon the fifth and sixth, and twenty-four 
upon the penultimate turn. The junctions of the axial ribs and spiral 
keels are somewhat tuberculated, while the spaces inclosed between them 
are deeply impressed pits. A strong keel marks the periphery of the last 
whorl and another equally strong occupies the middle of the base, the 
space between them being a concave channel, which, like the one posterior 
to the peripheral keel is crossed by the axial ribs. The axial ribs become 
much enfeebled as they pass over the basal keel and are almost obsolete on 
the spaces anterior to it. Aperture irregularly oval; posterior angle obtuse; 
outer lip thin, rendered angular by the spiral keels; columella very strong, 
almost straight, slightly reflected; parietal wall covered by a thin callus. 
Length, 6.7; diameter, 2.5 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 107422. Type locality, 
San Pedro, California. 
Range. San Pedro, California, to Scammons Lagoon, Lower Cali¬ 
fornia. 
Subgenus Miralda A. Adams, 1864 
Odostomia aepynota Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 178; PI. 19, fig. 5. 
Shell pupiform, translucent. Nuclear whorls small, obliquely im¬ 
mersed in the first post-nuclear turns, marked by four spiral cords. Post- 
nuclear whorls with the summits appressed, marked by two strong, spiral 
keels between the sutures, a third at the periphery, and a fourth on the 
middle of the base, the last two somewhat less strong than the rest. The 
[470] 
