218 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



OPI8THOSIPHON (OPISTHOSIPHONA) MAYNABDI Vanatta 



Plate 36, Figure 2 



1920. Opisthosiphon maynardi Vanatta, Proc. Acad. Nat. Sci. Philadelphia, vol. 

 72, pp. 204-205, pi. 6, figs. 9, 10, 11, 13. 



Shell moderately large, the early remaining whorls reddish brown, 

 the last flesh-colored, marked with faint interrupted spiral bands of 

 brown. Nuclear whorls decollated in all our specimens. Postnuclear 

 whorls well rounded, marked by weak, distantly spaced axial riblets. The 

 spaces separating these riblets are twice or more as wide as the riblets. 

 The riblets become expanded at the summit to form hollow tubercles. Of 

 the axial ribs, 58 occur on the last whorl in the type. Suture on the early 

 whorls narrowly channeled, less so on the last turn which is almost 

 appressed. Periphery well rounded. Base rather short, openly umbilicated, 

 marked by the continuation of the axial ribs and on the umbilical wall 

 by several weak spiral threads. Aperture oval; peristome double, the 

 outer very broadly expanded, a little wider on the inner lip, forming a 

 slight auricle at the posterior angle, and marked by rather strongly raised 

 concentric lamellae; inner peristome slightly exserted. Operculum typi- 

 cally opisthosiphonid. 



The specimen described and figured is one of five topotypes (U.S.N.M. 

 No. 426035) received from C. J. Maynard, who collected them at Nassau, 

 New Providence. It has 3.7 whorls remaining and measures: Length, 

 10.2 mm.; greater diameter, 5.5 mm.; lesser diameter, 5.0 mm. The 

 other 4 specimens yield the following measurements : 



OPISTHOSIPHON (OPISTHOSIPHONA) 8IMPSONI, new species 



Shell elongate-conic, varying in the various races from flesh-colored 

 through pale brown to roseate, unicolor or marked with interrupted 

 spiral bands of brown; the early turns are usually a little darker than 

 the later; the aperture varies with the external coloration, and so does 

 the peristome. Nuclear whorls almost 2, small, smooth except for the 

 last portion of the last turn, which shows the beginning of the post- 

 nuclear sculpture. Postnuclear whorls moderately rounded, narrowly 

 shouldered at the summit, marked by numerous, very fine, closely spaced, 

 slightly retractively slanting axial ribs, some of which become expanded 

 at the summit to form slender denticles. Suture narrowly channeled. Pe- 



