44 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.49. 



become obsolete on the ribs. Aperture small, chamieled anteriorly 

 and posteriorly; outer lip very thick; reinforced immediately behind 

 the edge by a strong varix; inner lip very thick, sinuous, appressed to 

 the base, the anterior portion being so arranged as to give the aperture 

 the appearance of having a truncated columella. 



The 2 cotyi^es and 9 other specimens, Cat. No. 46153, U.S.N.M., 

 come from the Gulf of Cahfornia. The young specimen of the two 

 cotypos shows the nuclear whorls. The adult has lost all the nuclear 

 turns, having 7 postnuclear whorls, which measure: Length, 6 mm.; 

 diameter, 2.2 mm. Cat. No. 46154, U.S.N.M., contains 9 specimens 

 from the Gulf of California. Cat. No. 46165, U.S.N.M., 4 specimens 

 from the same place. Cat. No. 23763, U.S.N.M., 3 specimens from 

 Mazatlan. Cat. No. 46153, U.S.N.M., 3 specimens from the Gulf of 

 Cahfornia. Cat. No. 59338, U.S.N.M., 20 specimens from Acapulco, 

 Mexico. Cat. No. 251588, U.S.N.M., 3 specimens from Puerto Angeles, 

 Oaxaca, Mexico. 



RISSOINA HELENA, new species. 

 Plate 28, fig. 2. 



Shell elongate-conic, yellowish white. (Nuclear whorls decollated.) 

 Postnuclear whorls moderately rounded, very weakly shouldered at 

 the summit, marked by very strong, shghtly protractivo axial ribs, 

 of which 14 occur upon the first, 16 upon the second, 18 upon the third, 

 and 22 upon the penultimate turn. Intercostal spaces about as wide 

 as the ribs, marked between the sutures by about 30 well incised 

 spiral striations, which are about as far apart as the spaces that sepa- 

 rate them, causing these to appear as slender lirations. Base moder- 

 ately long, well rounded, without fasciole, marked by the continua- 

 tions of the axial ribs which extend to the umbilical chink and numer- 

 ous spiral hrations, which are a little stronger here than on the spire. 

 Aperture small, slightly channeled anteriorly and posteriorly; outer 

 hp thick, reinforced immediately behind the edge by a thick varix; 

 inner lip thick, appressed to the/ l:)ase, thickening anteriorly in such 

 a way as to give the aperture the aspect of having a truncated 

 columella. 



The type and another specimen of this species. Cat. No. 149341, 

 U.S.N.M., come from Peru. The type has 6 postnuclear whorls and 

 measures: Length, 7.2 mm.; diameter, 3.1 mm. 



RISSOINA ID, new species. 



Plate 28, fig. 4. 



Shell large, elongate-conic, yellowish white. Nuclear whorls decol- 

 lated. Postnuclear whorls slightly rounded, almost flattened in 

 the middle between the sutures, weakly shoiddored at the summit, 

 marked by strong, rounded, shghtly sinuous, decidedly protractivo 



