CLASS GASTROPODA 
221 
Type in United States National Museum, No. 105488. Type locality, 
San Diego, California. 
Range. Known only from type locality. 
Cyclostrema miranda Bartsch, 1911 
Plate 105, figs. 1, 2, 3 
Proceedings of the United States National Museum, 39:230; PI. 39, figs. 1-3. 
Shell small, subdiaphanous, depressed. Nuclear whorls two, depressed 
helicoid, smooth. Post-nuclear turns one and a third, appressed at the 
summit, marked above with three strong, spiral cords, one of which is at 
the periphery, while the other two divide the space between the periphery 
and the summit into three equal areas. The space between the summit and 
the first spiral cord is decidedly concave, while the space between the first 
spiral cord and the median one is very slightly concave, that between the 
median and the peripheral cord being well-rounded. Axially, the upper 
surface of the shell is marked by about sixty-two slender, well-developed, 
equally spaced riblets, which are about half as wide as the spaces that 
separate them. These riblets are decidedly retractively curved between the 
summit and the first keel, less so between the first and the median keel, 
while between the median and the peripheral one they are practically ver¬ 
tical. The junctions of riblets and keels are not nodulose. Periphery of 
the last whorl strongly angulated; base marked by two spiral cords, one of 
which bounds the broad, open, funnel-shaped umbilicus and is a little 
weaker than the other, which appears as a very strong cord halfway 
between it and the periphery. In addition to these spiral cords, the base is 
marked by the undiminished continuations of the axial riblets which be¬ 
come bifurcated here and extend deep within the umbilicus. Aperture very 
large, ovate, very oblique, the columellar border being considerably behind 
the outer lip; the posterior and anterior angles are acutely angulated; outer 
lip thin, showing the external sculpture within ; columella slender, decidedly 
curved, the free edge continuing to the posterior angle of the aperture, 
rendering the peritreme complete. (Bartsch.) 
Type in United States National Museum, No. 211108. Type locality, 
San Pedro, California. 
Range. Known only from type locality. 
Cyclostrema baldridgae Bartsch, 1911 
Plate 105, figs. 7, 8, 9 
Proceedings of the United States National Museum, 39:229; PI. 39, figs. 7-9. 
Shell rather large, bluish-white, subdiaphanous. Nuclear whorls two 
and a third, smooth, forming a decidedly depressed spire. Post-nuclear 
[823 ] 
