NO. 2094. M0LLU8E8 OF THE 0ENU8 RISSOINA—BARTSCH. 41 



upon the third, 22 upon the fourth, 28 upon the fifth and sixth, and 

 30 upon the penultimate turn. These ribs extend prominently from 

 the summit of the whorls to the umbiHcus. Intercostal spaces a 

 Uttle wider than the ribs on the early turns, and about as wide on 

 the later, marked by exceedingly fuie and very numerous spiral 

 threads. Sutures shghtly sinuous. Periphery of the last whorl well 

 rounded. Base short, well rounded, marked by the continuation of 

 the axial ribs and about 13 spiral threads, which are much coarser 

 than those on the spire. Aperture very obUque, auriculate, shghtly 

 channeled posteriorly and anteriorly, somewhat effuse at the junction 

 of the basal and outer hp; outer and basal lip very much thickened 

 at the edge; columella short, with a decided notch at its junction 

 with the basal lip, reflected over and appressed to the base, where it 

 appears as a thick callus; parietal waU covered with a thick caUus, 

 which joins the outer lip and the columella. 



Thirty-one specimens of this species were collected by Professor 

 Adams under stones, near low-water mark, at Taboga, Panama, We 

 have figured two of these; the larger has 8 whorls and is minus the 

 nucleus, and measures: Length, 7.5 mm.; diameter, 3 mm. The 

 smaller has lost the first nuclear turn, and has 8 postnuclear whorls 

 and measures: Length, 6 mm.; diameter, 2.7 mm. In addition to 

 these two, 14 specimens of the type lot remain m the C. B. Adams' 

 collection at Amherst. The United States National Museum has one. 

 Cat. No. 204101, which was collected by the U. S. Bureau of Fisheries 

 steamer Alhatross on the beach at TaboquiUa Island, Bay of Panama, 

 and two additional specimens, Cat. No. 272937, from Panama. 



RISSOINA GISNA, new species. 



Plate 28, fig. 1. 



Shell of medium size, bluish white, elongate-conic. Nuclear 

 whorls 2^, well rounded, smooth, forming a pupoid apex. Post- 

 nuclear whorls short, trmicated, shouldered at the summit, moder- 

 ately rounded, marked by decidedly protractive, feebly curved axial 

 ribs, of which 14 occur upon the first, 16 upon the second to fourth, 

 18 upon the fifth and sixth, and 20 upon the penultimate turn. These 

 ribs extend prominently to the summit and render the sutures sinuous. 

 Intercostal spaces about two times as wide as the ribs, crossed by 

 exceedingly fine spiral striations. Sutures well marked. Base short, 

 moderately rounded, without fasciole, marked by the continuations 

 of the axial ribs which extend undiminished to the umbiUcal chuik. 

 The intercostal spaces and the ribs are crossed by 13 slender, equal, 

 and equally spaced, low, spiral cords which appear as coils of a 

 bandage, the posterior edge of which is free. The extreme anterior 

 portion of the base is free of spiral sculpture. Aperture small, chan- 

 neled anteriorly and posteriorly; outer Up thin within , reinforced 



