no. 1823. M0LLV8K8 OF THE GENUS CER1THT0P8I8—BART8CIT. 345 



by three nodulose, spiral cords which divide the spaces between the 

 sutures into four equal parts. In addition to the spiral cords, the 

 shell is marked with well-rounded, vertical, axial ribs which extend 

 from the summit to the suture and are as strong as the spiral cords, 

 rendering their intersections with them strongly tuberculate. Of 

 these ribs, 16 occur upon the first, 18 upon the second to fifth, and 

 24 upon the penultimate turn. The spaces inclosed between the 

 spiral cords and axial ribs are deep, squarish pits, except on the last 

 whorl, on which they are rectangular, having their long axes coin- 

 ciding with the axial ribs. In addition to the above sculpture, the 

 entire surface of the spire is marked by very fine lines of growth and 

 numerous microscopic, spiral striations. Suture well impressed, 

 in the last two turns showing the posterior edge of the peripheral 

 cord as a slender, raised thread. Periphery of the last whorl marked 

 by a strong, smooth, spiral cord; the sulcus which separates this 

 keel from the supraperipheral cord is crossed by the strong continua- 

 tions of the axial ribs. Base decidedly concave between the periph- 

 eral cord and the slender, basal f asciole which is at the insertion of the 

 columella; marked by rather strong lines of growth and fine micro- 

 scopic, spiral striations. Aperture broadly ovate; decidedly chan- 

 neled anteriorly; posterior angle obtuse; outer lip thin, rendered 

 sinuous by the external sculpture which shows strongly within; 

 columella short, very broad at base, curved and somewhat twisted; 

 parietal wall glazed with a thin callus. 



The type (Cat. No. 16196, U.S.N.M.) has seven post-nuclear whorls 

 and measures: Length 7 mm., diameter 2.4 mm. It was collected by 

 Xantus at Cape San Lucas, Lower California. 



CERITHIOPSIS (CERITHIOPSINA) NECROPOLITANA, new species. 



Plate 39, fig. 1. 



Shell almost cylindro-conic, creamy white. Nuclear whorls two, 

 a little wider than the first post-nuclear whorl succeeding them; 

 first half smooth, the rest marked by strong, slightly retractive, sub- 

 lamellar, axial ribs, of which 14 occur upon the first whorl and 17 

 upon the second. Post-nuclear whorls moderately rounded, orna- 

 mented with three spiral cords, the first of which is at some little dis- 

 tance below the summit, giving this a decidedly shouldered aspect, 

 while the third is an equal distance posterior to the suture, the second 

 being halfway between the two. In addition to the spiral cords, the 

 whorls are marked by vertical, axial ribs, almost equaling the spiral 

 cords in strength; of these ribs, 14 occur upon the first, 16 upon the 

 second to sixth, 18 upon the seventh, and 22 upon the penultimate 

 turn. The junctions of the axial ribs and spiral cords form strong, 

 cusp-like tubercles which are elongate on the first spiral cord, having 

 their long axes parallel to the spiral sculpture, and are suddenly 



