CLASS GASTROPODA 
97 
This shell is peculiarly ribbed. The eight upper whorls are strongly 
and somewhat obliquely ribbed; but on the last, which is the largest, the 
ribs are indistinct on the upper half, and on the lower half disappear 
altogether. The interstices between the ribs, which in the penultimate 
whorl are about sixteen in number, appear smooth. The sutures are deep 
and well-marked. The mouth is rather small, and is somewhat rounded- 
ovate. (Baird.) 
Type in British Museum. Type locality, Esquimalt Harbor, Van¬ 
couver Island. ‘‘Taken from the crop of a Pin-tail Duck.” 
Range. Port Etches, Alaska, to Puget Sound. 
Turbonilla attrita Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 46; PI. 4, figs. 11, 11a. 
Shell slender, elongate-conic, bluish-white. Nuclear whorls small, 
two and one-half, depressed, helicoid, having their axis at right angles to 
that of the succeeding turns, in the first of which they are slightly im¬ 
mersed. Post-nuclear whorls very high between the sutures, almost flat¬ 
tened, ornamented with very low, flattened, somewhat irregular, protec¬ 
tive axial ribs, which are best developed on the early whorls. Of these 
there are eighteen upon the second, twenty-two upon the third, eighteen 
upon the fourth and fifth, twenty-two upon the sixth, eighteen upon the 
seventh, twenty upon the eighth and ninth; on the next turn they be¬ 
come quite enfeebled, and on the penultimate turn they are obsolete. 
Intercostal spaces about half as wide as the ribs and very shallow. Sutures 
well-impressed. Periphery of the last whorl well-rounded. Base short, 
somewhat inflated. Entire surface of the spire and base marked by 
numerous very fine, wavy spiral striations. Aperture broadly oval; pos¬ 
terior angle acute; outer lip thin; columella short, slender, somewhat 
curved, and slightly reflected. Length, 7.4; diameter, 1.6 mm. (Dali 
and Bartsch.) 
Type in United States National Museum, No. 162248. Type locality, 
San Pedro, California. 
Range. San Pedro to San Diego, California. 
Turbonilla asser Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 45; Pi. 3, figs. 1, la. 
Shell elongate-conic, milk-white. Nuclear whorls small, two, de¬ 
pressed, helicoid, having their axis at right angles to that of the suc¬ 
ceeding turns, in the first of which they are about one-third immersed. 
Post-nuclear whorls well-rounded, slightly overhanging, ornamented by 
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