Akt. 11 NEW AMERICAN MARINE MOLLUSKS BARTSCH 25 



The type, Cat. No. 340826, U.S.N.M., was collected off O'Neal 

 Island, Puget Sound. It has 10.5 whorls and measures, length, 5.5 

 mm. ; diameter, 2.7 ram. 



The following additional specimens have been examined: Three 

 specimens, Nanaimo, British Columbia, Cat. No. 340841, U.S.N.M. ; 

 four specimens. Port Orchard, Puget Sound, Cat. No. 133233, 

 U.S.N.M. ; seven specimens, San Juan Island, Puget Sound, Cat. No. 

 340934, U.S.N.M. 



CERITHIOPSIS (CERITHIOPSroELLA) ONEALENSIS Bartsch 



Plate 5, flg. 2 



Cerithiopsis (Cerithiopsidella) onealensis Babtsch, Proc. Biol. Soc. Wash., 

 vol. 34, 1921, pp. 35-36. 



Shell elongate-conic, pale chestnut brown. Nuclear whorls decol- 

 lated in the type. In one of the three specimens of this species (Cat. 

 No. 346649, U.S.N.M.), collected by G. Willett at Craig, Alaska, the 

 last two nuclear whorls are present. These show slender, decidedly 

 retractively curved, rather distantly spaced, axial riblets between 

 which many even finer spiral threads are present. Postnuclear whorls 

 moderately rounded, slightly overhanging, crossed by very strong, 

 broad, rounded, slightly protractively slanting axial ribs, of which 

 16 occur upon the first four turns, 18 upon the fifth, and 26 upor- 

 the last. Intercostal spaces about half as wide as the ribs. In addi- 

 tion to the axial ribs the whorls are crossed by three strong spiral 

 cords, of which the one at the summit is a little less strong than the 

 other two. The junction of the axial ribs and spiral cords forms very 

 prominent tubercles. Those on the cord near the summit are well 

 rounded. Those on the median cord are truncated posteriorly and 

 almost truncated anteriorly, while those on the cord above the suture 

 are abruptly truncated posteriorly and slope moderately, gently 

 anteriorly. On the last whorl, where the ribs are much more crowded, 

 the tubercles have an oblong outline, and are about equal on all three 

 cords, their long axis coinciding with the axis of the shell. The 

 pits inclosed by the spiral cords and axial ribs are well rounded 

 on all the whorls. Suture strongly impressed. Periphery of the 

 last whorl marked by a sulcus about as broad as that separating the 

 median from the supersutural cord on the spire. Base short, well 

 rounded, marked by feeble continuations of the axial ribs, which 

 lend it a roughened aspect, and a single slender spiral thread, which 

 encircles the base at the insertion of the columella. Aperture de- 

 cidedly channeled anteriorly ; posterior angle obtuse ; outer lip thin, 

 showing the external sculpture within, sinuous at the edge ; inner lip 

 sigmoid, reflected over and appressed to the columella. 



