ANISOSPIRA. 29 



gular above (fig. 3), and the internal pillar is weakly spiral. 

 A weak keel-like ridge encircles it midway, visible even in the 

 fifth whorl from the last ; in the penultimate whorl it is more 

 conspicuous, but not very large. Under it, close to the par- 

 tition, there is a rather strong flattened lamella on the pillar, 

 which both increases and decreases rapidly (pi. 11, fig. 2). 



The Sumichrast shells from Tehuantepec (pi. 10, f. 22, 23, 

 25, 27; pi. 11, fig. 1) differ in the straighter axis, which is not 

 visibly sinuous, the much shorter and weaker median colu- 

 mellar cord, and perhaps the longer, less basally situated col- 

 umellar lamella. The aperture moreover is more nearly cir- 

 cular. These differences, however, are probably not specific, 

 but indicate local racial variation. 



A young shell of the Sumichrast lot (pi. 10, fig. 25), exam- 

 ined by Strebel, has the nucleus smooth, then fine sharp ribs 

 appear, which up to and including the third whorl are more 

 spaced than on following whorls, the total number of which 

 is 12. 



A. STREBELI Pf effer. PL 10, figs. 30-34 ; pi. 11, fig. 4. 



Shell rimate, fusiform-cylindric or more or less swollen, 

 solid and strong though not thick, grayish flesh- tinted or pink, 

 without gloss. Surface sculptured with fine, regular rib- 

 striae separated by intervals of double their width. Whorls 

 remaining 7 to 9, moderately convex, the last faintly or obso- 

 letely keeled, a slight depression which is sometimes brownish 

 just above the keel. Aperture oblique, produced shortly for- 

 ward, rounded-ovate. Peristome pale, obtuse or thickened, 

 narrowly expanded or sub-reflexed; columella straightened 

 within. Internal axis a little swollen in the middle within 

 each whorl and distinctly twisted in a weak spiral. This is 

 noticeably stronger within the penultimate whorl, where it is 

 accompanied by a second cord revolving immediately adja- 

 cent to the partition below. 



Length 50, diam. 15, length of aperture 11%, width 10 mm. 



Length 43, diam. 14, length of aperture 11, width 

 10 mm. 



Length 40, diam. 12, length of aperture 10, width 9 mm. 



