90 MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
tractive axial ribs, of which fourteen occur upon the second and third, 
sixteen upon the fourth to eighth, eighteen upon the ninth and tenth, 
twenty upon the eleventh, twenty-four upon the twelfth, and twenty-five 
upon the penultimate turn. On the early whorls these ribs are very 
strong in the middle, bending suddenly toward the summit, which gives 
them a decidedly angulated appearance a little below their termination; 
on the last three whorls they are more closely crowded and less strongly 
developed. Intercostal spaces about one and one-half times as wide as the 
ribs on the early whorls; on the last three they are about equal to them, 
well-impressed, terminating a little above the sutures. Sutures well- 
marked. Periphery of the last whorl slightly angulated. Base short, 
well-rounded. Aperture rhomboidal; columella slender, somewhat curved, 
and slightly reflected. Length, 8.1; diameter, 2 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 206851. Type locality, 
University of California Station 43, off San Diego, California. 
Range. Catalina Island to San Diego, California. 
Turbonilla aepynota Dali and Bartsch, 1909 
Plate 49, figs. 10, 10a 
Bulletin 68, United States National Museum, 35; PI. 2, figs. 10, 10a. 
Shell small, elongate-conic, diaphanous. Nuclear whorls two and one- 
half, small, helicoid, forming a moderately elevated spire, having their 
axis at right angles to that of the succeeding turns, in the first of which 
they are about one-fifth immersed. Post-nuclear whorls high between 
the sutures, very strongly shouldered at the summits, somewhat con¬ 
tracted at the periphery, well-rounded, marked by strong, sublamellar 
axial ribs that render the summits strongly crenulate. Sixteen of the 
axial ribs appear upon the first and second, eighteen upon the third, 
fourth, and fifth, and twenty upon the remaining turns. Intercostal 
spaces a little wider than the ribs, deeply sunk below the general sur¬ 
face, extending to the suture on all the turns of the spire. Sutures 
strongly marked. Periphery of the last whorl feebly angulated. Base 
short, well-rounded, smooth. Aperture rather large, subquadrate, pos¬ 
terior angle obtuse; outer lip thin, bent abruptly anteriorly toward the 
columella, which it joins almost at right angles; columella very slender 
and gently curved. Length, 3.2; diameter, 0.9 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 162443. Type locality, 
off San Martin Island, Lower California, in 30 fathoms. 
Range. San Pedro, California, to San Martin Island, Lower Cali¬ 
fornia. 
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