60 DENTALIUM-ANTALIS. 



Of Pacific species, D. numerosum Dall, a form which occurs in 

 very deep water from the Galapagos to California abundantly, has 

 the most general resemblance to the present species; but it grows to 

 nearly twice the length, and when closely examined is seen to have 

 a sharply pentagonal posterior section with a conspicuous ventral 

 slit. D. numerosum is a somewhat straighter and longer shell than 

 D. 'phaneum. (Dall). 



D. VARIABILE Deshayes. PI. 1 4, figs. 26, 27, 28. 



Shell rather small, moderately arcuate, not much attenuated pos- 

 teriorly, solid ; white, with numerous encircling grayish-translucent 

 zones, more pronounced on the rihs, which appear articulated with 

 grayish and white. Sculpture of 10 or 11 strong narrow ribs with 

 concave interstices, at and near the apex ; a median thread soon 

 arising in each interval, and becoming nearly equal to the primary 

 ribs, and later other interstitial riblets arise in some intervals, so that 

 at the aperture there are about 22, 24 or more riblets. Aper- 

 ture round, slightly polygonal. Anal orifice small and circular with 

 thick margin. No slit or notch. 



Length 19, diara. aperture 2, diam. apex 1"1 mill. 



Length 18, diam. aperture 2, diam. apex 1 mill. 



Mergui Archipelago at Mergui on mud-flats and Sullivan I. in 7- 

 10 fms. (Anderson) ; Philippine Is. (Sowb., Acad. CoU.) found at a 

 dealers with mainly small Indian shells (Desh.). 



D. variabile Desh., Mem. Soc. Hist. Nat. Paris, ii, p. 367, pi. 16, 

 f 30 (1825).— SowERBY, Thes. Conch., iii, p. 101, pi. 224, f. 30 

 (1860) ; Conch. Icon., xviii, pi. 4, f. 26 (1872).— Martens, Journ. 

 Linn. Soc. Lond., xxi, p. 200. Not D. variabile Costa or Risso. 



DiflTers from D. belcheri in being narrower and less rapidly en- 

 larging. The dotted ribs are characteristic, but their number varies 

 considerable. It sometimes reaches 30 mill, length. Compare D. 

 disparile Orb. 



D. belcheri Sowerby. PI. 14, figs. 29, 30. 



Shell subcylindrical, equally and closely ribbed, lightly curved 

 towards the apex ; white or roseate, with pale maculation on the ribs ; 

 apex entire and obtuse. (Sowb.). 



Length 32, greatest diam. 5 mill, (from fig.). 



Length 26, greatest diam. 4*5 mill, (from fig.). 



East Indian Archipelago (Sowb.). 



