NO. 2004. M0LLVHK8 OF THE GENU^ RISSOlNA—BARTtiCli. 59 



feebly channeled posteriorly; outer lip very thick and effuse, rein- 

 forced immediately behind the edge by a thick varix; imier lip 

 slender, curved and appressed at the base; parietal wall covered with 

 a thick callus which renders the peritreme complete. 



The type, Cat. No. 226456, U.S.N.M., was di^edgcd in 3 fathoms 

 off South Coronado Island. It has almost 5 postnuclear whorls 

 and measures: Length, 2.8 mm.; diameter, 1.2 mm. 



RISSOINA CERROSENSIS, new species. 

 Plate 33, fig. 5. 



Shell elongate-ovate, diaphanous. Nuclear whorls 2, well rounded, 

 smooth. Postnuclear whorls wcU rounded, appressed at the sum- 

 mit, smooth, exceptmg feeble hues of growth and an occasional 

 stronger tlu'ead. Suture moderately constricted. Periphery of the 

 last whorl well rounded. Base moderately well rounded, without 

 fasciole, marked hke the spire. Aperture rather large, decidedly 

 obUque, effuse at the junction of the outer and basal lijis, feebly 

 channeled anteriorly; outer lip thin; inner Hp strongly curved, 

 reflected over and adnate to the base; parietal wall covered with 

 a moderately thick callus. 



The type. Cat. No. 129318, U.S.N.M., was dredged by the U. S. 

 Bureau of Fisheries steamer Albatross at station 2983 in 58 fathoms 

 on sand bottom, bottom tem.perature 55°, off Cerros Island, Lower 

 California. It has 5 postnuclear whorls and measures: Length, 

 2.4 mm.; diameter, 1.2 mm. 



RISSOINA DALLI, new species. 

 Plate 33, fig. 2. 



Shell small, elongate-conic, subdiaphanous. Nuclear whorls 

 almost 2, inflated, well rounded, smooth. Postnuclear whorls 

 moderately rounded, appressed at the summit, the appressed por- 

 tion being somewhat excurved, lending the whorls the aspect of 

 having a double suture. Whorls marked by numerous, very fine, 

 closely spaced, almost vertical, axial thi'eads which are about as wide 

 as the spaces that separate them. Sutm-e feebly mipressed. Peri- 

 phery of the last whorl well rounded. Base moderately long, weU 

 rounded, marked like the spire. Aperture moderaly large, ovate; 

 outer lip somewhat effuse, thick at the edge, thm withm where the 

 external sculpture is seen tlu-ough the substance of the shell; iimer 

 lip moderately thick, strongly curved, reflected over and adnate to 

 the base. Parietal wall covered with a thick callus which renders 

 the peritreme complete. 



Cat. No. 107281, U.S.N.M., contains the type and 18 specimens 

 from San Pedro, Cal. The type has almost 6 postnuclear whorls 



