278 CALIFORNIA ACADEMY OF SCIENCES. 



last whorl to the umbilical region, and five very strong, broad, flat, subequally spaced spiral ridges, 

 which give the spire a reticulated, pitted pattern; the portions between the ribs and the spiral folds 

 appear as small, deep pits of a more or less circular outline, while the ribs appear thickened where 

 they are crossed by the spiral bands; a sixth spiral band maps out the path for the shoulder of the 

 succeeding whorl on the periphery of the basal whorl, while the base proper is marked by about 

 eight spiral striations, which are strongest at the periphery and gradually weaken toward the 

 umbilicus; the whorls are marked by a quite prominent sloping shoulder, which extends from the 

 first revolving band to the summit; the suture is deep, subchanneled; aperture broadly ovate, some- 

 what effuse, with the posterior angle acute; outer lip thin, crenulate by the spiral ridges, meeting the 

 curved and revolute columella in a broad curve; a thin callus extends from the posterior angle of the 

 aperture to the umbilical region. 



Dimensions. — Long. 6.8 mm.; diam. 2.2 mm. 



The specimen figured is from San Pedro, and has nine whorls. 



Post-Pliocene specimens from California are usnally larger, though quite 

 identical in every other respect. One of nine post-nuclear whorls measures: long. 

 8.6 mm.; diam. 2.4 mm. The smallest forms come from Lower California. One of 

 eight post-nuclear whorls measures: long. 4.9 mm.; diam. 1.6 mm. 



Section Pyrgolampros Sacco. 



Pyrgolampros Sacco, I Moll, del Piedmonte e della Liguria, p. 85, 1892. Type, P. mioperplicatulus 

 Sacco. 



Turbonillas with more or less weak axial ribs, which always almost disappear as they pass 

 over the periphery and base of the last whorl, and many very fine, faint spiral striations; columella 

 usually somewhat flexuous. 



297. Turbonilla (Pyrgolampros) lowei D. I- B., sp. nov. 



Plate I, Fias. 5 and 5a. 



Shell of medium size, light golden brown; nuclear whorls three, small, helicoid, partly 

 slantingly immersed; post-nuclear whorls very similar to those of T. vancouverensis Baird, in out- 

 line, moderately convex, strongly contracted at base and moderately so at the summit, bounded by a 

 prominent suture. The early whorls increase less rapidly in diameter than the later ones, and are 

 ornamented by more and weaker axial ribs than the later ones; these ribs slant toward the aperture; 

 beginning with the sixth whorl the shell assumes a more robust character, the whorls become broader 

 and are ornamented by twenty to twenty-two strong, somewhat flexuose, almost vertical axial ribs, 

 which extend faintly over the angular periphery of the last whorl to the umbilical region; the entire 

 shell is traversed by many very fine, very closely placed spiral stri:e; aperture subrhomboid, outer lip 

 thin, produced and flaring at its junction with the twisted and revoluted columella. 



Dimensiotis. — Long. 7.2 mm.; diam. 2.2 mm. 



The type is from San Pedro, and has ten and one-half whorls. Sjiecimens 

 from the post-Pliocene of California are larger and more robust. One of ten normal 

 whorls measures: long. 8.1 mm.; diam. 2.4 mm. Fossil specimens occur abundantly 

 at San Pedro and San Diego. 



This species is named in honor of Mr. H. N. Lowe, of Long Beach, Califor- 

 nia, to whom we are indebted for material bearing on our study of these difficult 

 little shells. 



