OXYCHONA. 181 



present one differs in being striped with brown on a fleshy or pink 

 ground instead of "crerulescenti-albida" : the outer lip is not ex- 

 panded, but the columellar lip is decidedly so, and it is distinctly 

 narrower in proportion. Pfeiffer's measurement of the diameter of 

 Bulimi was taken from the greatest convexity of the body-whorl on 

 the left side directly across, and not including the expansion of the 

 aperture below the level of a line so drawn ; but even thus, B. cceru- 

 lescens has a diameter of 12? mill, with a height of 31, while the 

 species here described measures only 11 mill, "overall" with a 

 length of 33 mill. It is likely therefore that this is a distinct 

 species. 



The color stripes on the spire run more nearly vertical than the 

 growth striae. Figure 35 is somewhat faulty in showing the outer 

 lip too arcuate; it is straighter in the middle and more suddenly 

 curved near the two ends. 



Genus OXYCHONA Morch, 1852. 



= 0xychona (Brazilian species only) PILSBRY, Man. of Conch. 

 (2), v, p. 128 ; ix, p. 189; Nautilus xi, p. 87 (1897). 



Shell trochiform with conspicuous peripheral keel and flattened 

 whorls, smoothish, shining, and iraperforate ; aperture oblique, 

 angular, with expanded or reflexed lip. Nepionic whorls regularly 

 latticed or with stronger vertical riblets. Jaw thin, arcuate, with 

 numerous unequal vertical riblets (see vol. ix, pi. 51, f. 11). Radula 

 peculiar, resembling that of Zaplagius (see vol. ix, p. 189, pi. 51, f. 

 9, 10, 0. bifasciata}. 



Distribution, Brazil ; type 0. bifasciata Burrow. 



The extraordinary resemblance of the dentition and nepionic 

 sculpture seem to indicate unmistakably a position for this group 

 in the genus Drymceus ; or at least immediately adjacent thereto, if 

 the general form of the shell and the somewhat different jaw beheld 

 sufficient for generic distinction. The Mexican and Central Amer- 

 ican species formerly associated with Oxychona have smooth apices, 

 and will be left in the Helicidce under the generic name Leptarionta 

 Crosse & Fischer. Even H. zhorquinensis, which so closely resem- 

 bles 0. bifasciata, has the smooth apex of Leptarionta. 



A key to the species will be found in Vol. V, pp. 129-131, with 

 descriptions and figures of bifasciata Burrow, lonchostoma Mke., 

 gyrina Val., &ud pileiformis Moric. (c/. Dohrn, Jahrb., x, p. 352). 



The apices of bifasciata (pi. 33, fig. 40, and fig. 41 x 100), and 

 of pileiformis (pi. 33, fig. 42), are here illustrated. 



