NO. 2094. MOLLUSKS OF THE GENV8 RISSOINA—BARTSCE. 53 



turn. These ribs become slightly attenuated near the summit, fre- 

 quently fusing there, with the ribs of the preceding turn. Intercostal 

 spaces about three times as wide as the ribs; marked bylines of growth 

 only. Sutures well impressed. Periphery of the last whorl well 

 rounded. Base somewhat produced, marked by the continuations 

 of the axial ribs, which fuse at the columella and there form a some- 

 what tumid area. Aperture oval; slightly channeled at the posterior 

 angle and at the junction of the columella and the outer lip; outer 

 lip remforced by a thick callus immediately behind the edge; col- 

 umella short, very thick, and somewhat reflected and appressed to 

 the base; parietal wall covered with a thick callus which renders 

 the peritreme complete. 



The type and 12 specimens, Cat. No. 266595, were dredged by the 

 author in shallow water in San Francisquito Bay, Gulf of California. 

 The type has 6 jDOstnuclear whorls and measures: Length, 3.7 mm.; 

 diameter, 1.6 mm. 



In addition to these, the following specimens, all dredged by the 

 author in the Gulf of California, are in the collection of thelJ. S. N. M. : 



Cat. No. 267155, 1 specimen from the same locality; Cat. No. 

 264653, 1 specimen from the head of Concepcion Bay; Cat. No. 

 267623, 5 specimens from head of Concepcion Bay; Cat. No. 267662, 

 an additional specimen from same locality; Cat. No. 265940, 16 

 specimens from Mulege; Cat. No. 266287, 2 specimens from Agua 

 Verde Bay. 



RISSOINA NfiREINA, new species. 

 Plate 32, fig. 1. 



Shell small, elongate-conic, milk white. Nuclear whorls 3, de- 

 cidedly rounded, scarcely increasing in diameter, forming a pupoid 

 apex. Postnuclear whorls well rounded, increasing regularly in size, 

 feebly shouldered at the summit, marked by strong, retractive axial 

 ribs wliich are about one-half as wide as the spaces that separate 

 them. Of these ribs, 14 occur upon the first and second, 16 upon the 

 third, 18 upon the fourth, and 22 upon the penultimate turn. Inter- 

 costal spaces well impressed, smooth. Suture strongly impressed, 

 slightly sinuous. Base of the last whorl somewhat prolonged, mod- 

 erately rounded, marked only by the continuations of the axial ribs 

 which extend prominently to the umbilical area. Aperture large, 

 feebly channeled anteriorly and posteriorly; outer lip thickened at 

 the edge, thin deep within, where the external sculpture may be seen 

 by transmitted light; a strong varix reinforces the outer lip immedi- 

 ately behind its edge. Imier lip thick, slightly sinuous, appressed 

 to the base, rendering the peritreme complete. 



The type and eight additional specimens were obtained in shell 

 washings at Point Abreojos, Lower California. The type has 5| post- 

 nuclear whorls and measures: Length, 4.3 mm.; diameter, 2 mm. 



