572 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



short, twisted, and truncated anteriorly to resemble a fold ; a strong, 

 oblique fold encircles the insertion of the columella; parietal wall 

 covered by a thin callus. 



The type (Cat. No. 216840, U.S.N.M.) and six specimens of this 

 species were collected by Mr. James Zetek at Panama City, Panama. 

 The type measures — ^length, 2.5 mm. ; diameter, 1.2 mm. 



ODOSTOMIA (CHRYSALLIDA) ZETEKI, new species. 



Plate 88, fig. 5. 



Shell of medium size, elongate-ovate, bluish-white. Nuclear whorls 

 deeply immersed in the first of the succeeding turns, which gives the 

 apex a truncated appearance; postnuclear whorls appressed at the 

 summit, the later ones overhanging, marked by exceedingly strong, 

 very distantly spaced axial ribs, of which 16 occur upon the second and 

 third, 14 upon the fourth, and 12 upon the penultimate turn. These 

 ribs are well rounded and have a slightly retractive slant. The spiral 

 sculpture consists of five raised bands, which are a little wider than 

 the spaces that separate them. The first of these is at the appressed 

 summit of the whorls, while the fifth is immediately posterior to the 

 angulated periphery (for in the adolescent stage, as shown by the 

 overhanging portion of the whorls the periphery is angulated, though 

 this is not the case in the last whorl of the adult shell), while these 

 raised threads pass upon the sides of the ribs they do not pass over 

 their summit in sufficient strength to render these tuberculated. The 

 spiral pits between the axial ribs and spiral threads appear as oblong 

 impressions, their long diameter being parallel with the spiral sculp- 

 ture. Suture rather poorly marked, not at all channeled. Periphery 

 of the last whorl well rounded. Base slightly produced, well rounded, 

 narrowly umbilicated, marked by the continuations of the axial ribs, 

 which extend feebly almost to the umbilical region, and eight spiral 

 threads, of which the first two below the periphery are as strong as 

 those occurring on the spire, while the rest become successively weaker 

 and more flat anteriorly. Aperture ear-shaped; posterior angle de- 

 cidedly channeled; outer lip thin and slightly reflected; inner lip 

 curved, somewhat sinuous and slightly reflected over the umbilicus; 

 parietal wall covered by a very strong callus, which is free at the 

 edge and renders the peristome complete by connecting the posterior 

 angle of the aperture with the insertion of the columella. 



The type (Cat. No. 216905, U.S.N.M.) was collected by Mr. Zetek 

 at Panama City, in sand siftings and rock washings at low-water 

 mark. It has 5.8 postnuclear whorls and measures — length, 2.8 mm. ; 

 diameter, 1.3 mm. 



This species is at once distinguished from all the others so far 

 described from the West Coast by its very strong axial ribs, which 

 are more distantly spaced than in any other form. 



