334 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



to the summit, the second median, and the third a little posterior to 

 the suture. In addition to the spiral cords, the whorls are marked 

 by retractive axial ribs which are almost as strong as the spiral 

 cords. Of these ribs, 16 occur upon the second, 18 upon the third, 

 and 20 upon the penultimate whorl. The junctions of the axial ribs 

 and the spiral cords form prominent tubercles, while the spaces 

 inclosed between them are elongated pits on the second whorl and 

 well-rounded, well-impressed pits on the remaining ones. Sutures 

 channeled. Periphery of the last whorl marked by a deep sulcus 

 which is crossed by the continuations of the axial ribs which extend 

 to the posterior edge of the first basal cord. Base moderately long, 

 concave in the middle, marked by eight low, rounded, subequally 

 spaced, spiral cords, which grow successively weaker from the periph- 

 ery toward the tip of the columella. Aperture irregular, decidedly 

 channeled anteriorly; posterior angle acute; outer lip rendered 

 sinuous at the edge by the external sculpture; columella moderately 

 long, twisted, the edge reflected, and joined to the posterior angle of 

 the aperture by a strong callus winch covers the parietal wall. 



The type, which is on Tablet No. 2032, Liverpool collection, British 

 Museum, has five post-nuclear whorls and measures: Length 1.6 mm., 

 diameter 0.7 mm. It and three additional specimens were found on 

 Spondylus at Mazatlan. 



CERITHIOPSIS (CERITHIOPSIS) CARPENTERI, new species. 

 Plate 38, fig. 9. 



Shell broadly elongate-conic, dark chocolate brown. Nuclear 

 whorls three, smooth, well rounded, separated by a slender suture, 

 forming an elongate-conic spire. Post-nuclear whorls well rounded, 

 marked by three strong, broad, spiral bands which are as wide as the 

 spaces that separate them. Of these, the first and widest is at the 

 summit, the next is median, while the third is a little posterior to the 

 suture. In addition to the spiral keels, the whorls are marked by 

 slender, rounded, axial ribs which are about half as wide as the spiral 

 cords. Of these ribs, 20 occur upon the first and second, 22 upon the 

 third to fifth, 24 upon the sixth and seventh, 28 upon the eighth, and 

 30 upon the penultimate turn. The junctions of the axial ribs and 

 spiral cords form strong, elongated tubercles, having their long axes 

 parallel with the axial sculpture. The tubercles at the summit are 

 well rounded anteriorly and posteriorly; those of the median series are 

 a little more suddenly rounded anteriorly than posteriorly; while those 

 belonging to the supraperipheral cord are truncated suddenly pos- 

 teriorly and slope gently anteriorly. The spaces between the spiral 

 cords and axial ribs are small, moderately rounded, well-impressed 

 pits. Suture constricted, showing a portion of the basal cord. 

 Periphery of the last whorl marked by a deep, spiral groove as wide as 



