182 MEGASPIRA. 



decidedly tapering, 33-35 mm. long, 7.5 wide 

 above the aperture, with 16-18 whorls; umbili- 

 cal fissure narrow M. elatior, no. 2. 



b. Columella similar; shell more cylindric and 

 slender, about 36 x 7 mm., with 18% to 19!/2 

 whorls ; umbilicus minute. M . e. gracilis, no. 2b. 



c. Larger and stouter, with wider umbilical fis- 

 sure; columella distinctly 3-folded. 



M. e. robusta, no. 2a. 



2. Baso-axial radial laminae low, few or none of them 

 hooked; external sculpture finer; columella bipli- 

 cate, the lower fold bifid; umbilical crevice minute; 

 length 37 to 39, diam. above aperture about 8 mm., 

 whorls 19 to 21. M. elata, no. 3. 



1. M. RUSCHENBERGIANA * Lea ' Jay. PL 28, figs. 1, 2, 3, 4. 

 Shell openly rimate-perforate, cylindric-tapering, rather 

 solid ; yellowish, variegated with red-brown streaks and spots. 

 Sculpture of oblique rounded riblets as wide as their inter- 

 vals, the latter more or less wrinkled across; about 3 riblets 

 in the space of 1 mm.; 3 apical whorls very finely striate, 

 usually worn in adult shells. Whorls 22 to 24, slightly con- 

 vex. Aperture slightly oblique, irregularly ovate. Peristome 

 thin, expanded, the columellar margin dilated and reflexed 

 above, notched at, and a short distance below, the insertion. 

 Columella convex, bearing three entering lamellae. Parietal 

 wall with a strong entering lamella. Axis perforate but slen- 

 der throughout. Columellar lamella wide and scalloped in 3 

 whorls preceding the last whorl, the scallops bent downwards ; 

 in the last whorl and the median and upper whorls it is re- 

 duced to a smooth, rather small lamella. The sub columellar 

 lamella penetrates inward as far as the enlarged portion of 

 the columellar, running on the lower side of the latter. The 

 supracolumellar lamella penetrates as a low cord about two 

 whorls. Baso-axial radial barriers begin in the fourth whorl 

 from the last ; are high, curved, with the upper edge bent for- 

 ward, and hooked at the axial end. The next to the last 

 barrier, in the back of the penult, whorl, is continued in a 



