262 PALAEONTOLOGY OF CALIFORNIA. 



pressed ; transverse section subcircular to subelliptical, the two 

 varices being nearly linear or obsolete in the young; and rough, 

 prominent, and sometimes imbricating in the adult. Aperture 

 elongate, acute behind, narrowly rounded in advance ; outer lip 

 simple or slightly thickened. In one very small specimen, the 

 inner surface of the outer lip shows a minute crenulatiou, that I 

 have been unable to detect in any other specimens of a large 

 series. Inner lip slightly incrusted. Surface marked by lines 

 of growth, and by the variable varices. 



Figures 6 and 6 c, natural size. Figure 6, from an average specimen, 6 c, from 

 an old shell, a top view to show the extreme form of the varices; 6 a and 6 b, front 

 and top views, magnified, from a young shell, showing the internal crenulation 

 and the symmetrical form. : ; ' 



One of the most common fossils at Arivechi. 



ANCHURA, Conrad. 



A. MONILIFERA, 11. S. 

 PI. 35, Fig. 7. 



SHELL small, elongate, slender, fusiform; spire elevated; whorls 

 numerous (six or seven?), rounded on the sides; body whorl 

 regularly rounded, never angulated except in some instances near 

 the origin of the large lip, where a faint carina starts and runs 

 out in the middle of the lip. Surface ornamented by numerous, 

 slightly flexuous, rounded ribs, with equal, concave interspaces, 

 ribs and spaces alike crossed by about a dozen sharply elevated 

 revolving threads. Outer lip unknown; the posterior angle of 

 the mouth reaches almost to the penultimate suture, and both 

 posteriorly and on the inner lip the aperture is bordered by a 

 rather broad and somewhat flattened plate. Anterior canal 

 unknown. 



Although this shell is quite common ; among perhaps fifty specimens, there was 

 not a single one showing more of the outer lip, or of the canal, than is illustrated 

 in the figure. 



