30 



Diagnosis. Shell thin, very narrow, acuminate, polished, subpellucid, little arcuate ; 

 lluted with about 14 ribs, which are not equidistant, only slightly elevated, but distinctly defined 

 at their bases; ribs at the apex coalescent and vanishing; interstices shallow and polished. 

 Length 31 mill., diam. at base 1,6 mill. (Cooke). 



Dist ri b i! tic n. Gulf of Suez. (Mac-Andrew). 



R e m a r k s. Of the three Siboga specimens two are rather young shells and show the 

 greatest resemblance to the t)pe in the Mac-Andrew collection at Cambridge, also a young 

 shell. The third seems much older. It is longer, less attenuated and the apex is ribbed not 

 smooth as in the other specimens. It has a length of 42 mill., with a greatest diam. of 2,1 mill. 

 Anteriorly the tube is rather irregular, many circular constrictions indicating interrupted growth, 

 while the ribs become nearly obsolete ; growth striae rather conspicuous. Cookei is probably 

 nearly related to sintios7iiu \ it is however more slender and distinguished by its smooth apex 

 and unequidistant ribs. 



30. DentaluDu pliiricostatjtm n. sp. PI. VI, figs 6, 7. 



Stat. 153. 0° 3.8N.. 130° 24'. 3 E. Bougainville Strait. 141 Metres. Fine and coarse sand with 



dead shells. 6 Spec. 

 Stat. 204. 4° 20' S., 122° 58' E. Buton Strait. From 75 — 94 Metres. Sand with dead shells. 



I Spec. 



Diagnosis. Shell long and slender, moderately curved, fragile. Sculpture of nine sharp 

 ribs at the top, separated by flat interstices, which appear to be microscopically longitudinally 

 striated when strongly magnified. The striae disappear rapidly, and not far from the apex a 

 secondary riblet appears in each interval, sometimes foliowed by a third and fourth and continuing 

 together with the primary ribs for about the greatest half of the shells length. Thej' then 

 become obsolete, the anterior half of the shell being nearly smooth, with only faint indications 

 of longitudinal sculpture. Growth striae rather conspicuous, microscopically segmenting the 

 intervals. Apex without slit or notch. Aperture round, very little oblique, with extremely thin 

 edges. Colour near apex white or yellowish-white, toward aperture white and transparent often 

 with a pearly lustre. 



a. Length 60 mill., greatest diam. 3,5 mill. 



b. Length 65 mill., greatest diam. 3,5 mill. 



c. Length 52 mill., greatest diam. 3 mill. 



*3i. Dentaliuin Lessoni Deshayes. PI. I, fig. 11. 



1825. Dentaliuin Lessoni Deshayes, Mém. Soc. Hist. Nat. Paris II, p. 357, pi. 16, fig. 13. 



? Dentalium Lessoni Deshayes. Chenu, Illustr. Conchyl., p. 5, pi. 5, fig. 4 (not 4«). 

 1897. Dentalium I-^essoni Deshayes. PiLSBRY & Sharp, Man. of Conch., vol, XVII, p. 8, pi. 6, 



figs 86, 90. 

 Not Dentalium lessonii Sowerby, 1860, 1872. 



Diagnosis. Shell rather straight, cylindrical, whitish-gray, with 8 to 10 ribs, ribs obtuse. 

 depressëd, disappearing at the aperture. Allied to D. noveincostatnii!^ but distinguished bj- form, 



