NO. 2094. MOLLUSKS OF THE GENUS RISSOINA—BARTSCH. 49 



somewhat sinuous, rounded ribs which are much wider than the spaces 

 which separate them, on the later whorls. On the first three turns 

 the intercostal spaces are about twice as wide as the ribs. Of these 

 ribs 16 occur upon the fij'st and second, 18 upon the thhd, 24 upon 

 the fourth, 30 upon the fifth, and 38 upon the sixth and ^penultimate 

 whorl. The intercostal spaces are crossed by spiral lirations, of 

 which three occur between the summit and the shoulder on the first 

 three turns and three between the shoulder and the base of the same 

 turns. These spiral threads become less strong on the succeeding 

 turns, and more closely spaced. On the last whorl 15 are present 

 between the summit and the periphery. The spiral threads are not 

 quite as wide as the spaces that separate them. Sutures moderately 

 impressed. Periphery of the last whorl slightly angulated. Base rather 

 short and well rounded, marked by the contmuations of the axial 

 ribs, and 20 spiral cords which become successively stronger from the 

 periphery to the umbilical area. Aperture very oblique, decidedly 

 channeled at the posterior angle and at the junction of the columella 

 and the basal lip; outer lip decidedly twisted, reinforced immediately 

 behind the edge with a thick callus, posterior portion drawn forward 

 into a claw-shaped element; columella short, twisted, reflected over 

 and appressed to the base ; parietal wall covered with a thick callus, 

 which renders the peritreme complete. 



The type and 106 specimens of this species. Cat. No. 267666, were 

 dredged by the author at the head of Concepcion Bay, Lower California, 

 in 2 to 4 fathoms of water. The type has 8 i)ostnuclear whorls and 

 measures: Length, 7 mm.; diameter, 3 mm. 



RISSOINA KELSEYI Dall and Bartsch. 



Plate 30, fig. 4. 



Rissoa kelseyi Dall and Bartsch, The Nautilus, vol. 16, 1902, p. M=Alaha 

 oldroydi Dall, The Nautilus, vol. 19, 1905. p. 15, 



Shell cylindric-conic, varying in color from yellow to light red, 

 unicolor or longitudinally streaked. Nuclear whorls 2, well rounded, 

 smooth. Postnuclear whorls slightlj/' shouldered at the summit, 

 marked by obsolete, broad, rounded, low, axial ribs, of which 12 

 occur upon the first and second, and 14 upon the third and fourth, 

 while on the penultimate whorl .they are altogether wanting. In 

 addition to the axial ribs, the whorls are marked by strongly incised, 

 spiral lines, which are a little closer spaced at the summit of the 

 whorls than at the suture. Of these, 15 occur upon the tliird, and 

 22 upon the penultimate turn between the sutm'es. Suture moder- 

 ately constricted. Periphery of the last whorl well rounded. Base 

 moderately long, well rounded, marked like the spire by about 10 

 subequal and irregularly spaced, incised, spiral lines. Apertm'e 

 irregularly oval, oblique; posterior angle obtuse; outer lip thick; 

 81022°— Proc.N.M.vol.49— 15 i 



