40 DENTALIUM-ANTALIS. 



Key to species. 



I. Shell becoming round and nearly smooth toward aperture, 

 sharply arid finely striate longitudinally toward apex, at least 

 in the young. 



a. Very fine longitudinal striae throughout, sharp threads on 

 on smaller end. 



b. No apical notch, the orifice simple or tubular, 



vulgar e, p. 41. 



b'. An apical notch; more than half the length sharply 

 striate, weinJcauffii, p. 40. 



a'. Only circular striae on larger part of the shell ; apex with 

 a short sheath and v-like notch, or simple, 



entalis, p. 42 ; pretiosum, p. 44 ; agile, p. 46. 



II. Shell with numerous riblets toward apex, persistent or becoming 

 obsolete near aperture. 



a. About 12 riblets at apex, becoming lower and double as 

 many and sometimes obsolete near aperture, 



occidental, p. 47. 



a'. 26-28 narrow ribs throughout, no interstitial riblets or 

 striae, cenigmaticum, p. 49. 



D. WEINKAUFFI Dunker. PI. 2, fig. 26. 



Shell large, solid, the smaller third well curved, the remainder 

 slightly so ; stout ; the length about 11 times the diam. of aperture ; 

 apical end not much attenuated. Flesh-colored, fading to whitish 

 toward the mouth ; shining. Sculpture, 16 narrow longitudinal 

 threads at apex, indistinctly alternating larger and smaller, and increas- 

 ing to about double that number at the end of the first third of the 

 shell's length. These threads are most prominent at the smaller 

 end, and gradually decrease in size, obsolete on the larger third of 

 the shell, where microscopic, superficial longitudinal striae replace 

 them. Growth- strioz conspicuously developed and irregular on the 

 larger half of the tube. Aperture circular, oblique, with thin per- 

 istome, the interior white, becoming yellow far within. Anal open- 

 ing small, narrowly ovate, passing into a small y-shaped notch on the 

 convex side. 



Length 80, diam. aperture 7'3, diam. apex 2 mill, (specimen). 



Length 86-87, diam. 8 mill. (Dkr.). 



Bishiu coast, Japan (Stearns). 



