386 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 40. 



been reported from the Upper Pliocene, Fernando Formation, at 

 Bath-house Beach, Santa Barbara, and the Pleistocene of Santa 

 Barbara, San Pedro, and San Diego, California. 



The remaining four — 

 Bittium armillatum Carpenter, Bittium giganteum Bartsch, and 



Bittium ornatissimum Bartsch, Bittium rugatum Carpenter, 



are from the Pleistocene of California. Their distribution is noted 

 after their description in the text. 



The illustrations accompanying this paper * are after photographs 

 made by Mr. T. W. Smillie, and were retouched by Mr. R. Weber. 



BITTIUM (BITTIUM) PANAMENSE, new species. 



Plate 53, fig. 5. 



Shell large, elongate-conic, brown, variegated with whitish areas. 

 Nuclear whorls small, partly decollated, a little more than one, smooth, 

 the remaining portion with two spiral lirations. Post-nuclear whorls 

 marked by feeble spiral cords which are a little stronger on the early 

 whorls than on the later ones. Three of these cords occur upon each 

 of the first five whorls, while on the sixth turn a fourth makes its 

 appearance at the summit; this rapidly increases in strength and 

 soon equals the other three. In addition to the spiral cords, the 

 whorls are marked by axial ribs which are much more strongly 

 developed on the early whorls than on the later ones. On the later 

 whorls they are merely indicated by the tubercles resulting from the 

 junctions of the cords and ribs. The tubercles are truncated ante- 

 riorly and slope gently posteriorly. Moderately strong varices occur 

 at irregular intervals. On the last two whorls a slender spiral thread 

 makes its appearance in the middle between the median tubercles 

 and also in the space between the two anterior cords. Sutures 

 weakly impressed. Periphery and base of the last whorl moderately 

 long, well rounded, marked by ten spiral cords which are truncated 

 posteriorly and slope gently anteriorly. These cords decrease regu- 

 larly in size from the periphery to the columella, over which the last 

 three extend. In addition to this sculpture, the entire surface is 

 marked by numerous fine lines of growth and exceedingly fine, spiral 

 striations. Aperture moderately large, irregularly ovate, decidedly 

 channeled anteriorly; posterior angle obtuse; outer lip thin, showing 

 the external sculpture within, which renders the margin sinuous; 

 columella short, stout, twisted, and very strongly reflected; parietal 

 wall glazed with a thin callus. 



1 In the preparation of the present diagnoses the following terminology is used: 



"Axial sculpture," the markings which extend from the summit of the whorls toward the umbilicus. 



The axial sculpture may be— 



"Vertical," when the markings are in general parallelism with the axis of the shell. 



" Protractile," when the markings slant forward from the preceding suture. 



" Retraclive," when the markings slant backward from the suture. 



"Spiral sculpture," the markings following the directions of the coils of the whorls. 



