NO. 1S63. MOLLVSKS OF THE GENUS ALVAXIA—BARTSCH. 361 



with the axial sculpture. On the last whorl an additional spiral 

 cord renders the pits between this cord and the next spiral cord and 

 the axial ribs also squarish. Suture strongly constricted. Periph- 

 ery of the last whorl marked by a sulcus as wide as that separating 

 the suprasutural cord from the one adjacent to it anteriorly. Base 

 well rounded, strongly umbihcated, marked by four equal and 

 almost equally spaced spiral cords, wdiich are as strong as those 

 occurring between the sutures and the feeble continuations of the 

 axial ribs. Aperture subcircular; outer lip thickened all around by 

 a very tliick varix; inner lip stout, decidedly curved, somewhat 

 reflected over and appressed to the base; parietal wall covered with 

 a very thick callus, wliich renders the peritreme complete. 



The type and another specimen (Cat. No. 213699, U.S.N.M.) 

 come from San Pedro, California. The type has three post-nuclear 

 whorls, and measures: Length 1.6 mm., diameter 1.05 mm. Cat. 

 No. 152193a, U.S.N.M., contains one specimen from San Pedro, 

 California; and Cat. No. 226454, U.S.N.M., two from 3 fathoms, off 

 South Coronado Island. Ten more from the same locaUty are in 

 Doctor Baker's collection. 



Named for Mrs. T. S. Oldroyd. 



ALVANIA TUMIDA Carpenter. 

 Plate 32, fig. 2. 

 Alvania tumida Carpenter, Cat. Maz. Shells, 1856, p. 360. 

 Shell minute, subglobose, chestnut brown excepting the columella 

 and the edge of the outer lip, which are light 3^ellow. Nuclear whorls 

 one and one-third, well rounded, very minutely papillose. Post- 

 nuclear whorls inflated, slopingly shouldered at the summit, well 

 rounded, ornamented with slender, almost vertical, axial riblets, of 

 which 24 occur upon the first and 30 upon the penultimate turn. 

 In addition to the axial riblets, the whorls are marked b}^ four spiral 

 cords, of which the first, which is at the summit, is very feeble; the 

 remaining three, which equal the axial ribs in strength, divide the 

 space between the sutures into four equal parts. The spaces inclosed 

 between the axial riblets and the spiral cords are squarish pits, while 

 their junctions are very feebly, roundly tuberculate. Suture moder- 

 ately constricted. Periphery of the last whorl marked by a slender 

 spiral thread, equaling those between the sutures in strength. The 

 space between it and the suprasutural cord is crossed by the con- 

 tinuations of the axial riblets. Base narrowly umbihcated, w^eU 

 rounded, slightly inflated, marked by tw^o spiral cords which equal 

 the peripheral one. The spaces between the cords are about four 

 times as wide as the cords and are crossed by the continuations of the 

 axial riblets. The umbilical chink is bordered b}^ a narrow tumid 

 area. Aperture subcircular; outer lip thick at the edge, reenforced 

 by a varix; inner lip decidedly curved, somewhat reflected over, and 



