7 



or. Shell transversely ribbed, especially near the apex Plagioglypta. p. 55 



a?. Small shells, extremely attenuated, or truncated with a small 



accessory tube Episiphon . p. 46 



a*. Shell cylindric, smooth or with deeply incised growth lines; a 



long slit on the convex side Fustiaria. . p. 58 



a". Shell cylindric, quite smooth, or with numerous low annular swellings. Laevidentalmm . p. 5 i 

 «". Shell smooth, solid, slightly notched on the convex side with a 



short supplemental tube Antalis . . p. 43 



Dentaliuni s. s. is divided into the following groups : 



Dark green or strongly coloured species, with 8 — 17 strong ribs. Group o{ D. elephantinum. 



Hexagonal at and near the apex Group of D. hexagonum. 



Sevenribbed at and near the apex Group of D. katoivense. 



Octagonal at and near the apex Group of D. octangu latum. 



Six to fourteen-ribbed at and near the apex Group of D. disexangii latum. 



Fourteen to twenty-one ribs at and near the apex Group of D. shoplandi. 



Small forms, finely striated, often with alternating translucent 



and opaque bands on the riblets Group of D. vniltistriatum. 



Group of D. ELEPHANTINUM. 



Shell solid, decidedly coloured, generally green, with 8 — 17 strong longitudinal ribs. 

 Ribs generally stronger on the concave side. Apex with or without notch. 



I. Greatest diam. about '/d the total length. 



a. -Shell dark green, pale at apex with about 10 ribs elephantinum. 



b.. Shell red, green and white with 13 — 16 strong ribs forniosum. 



II. Greatest diam. about V12 the length. 

 a. 8 — -13 longitudinal continuous ribs. 



b interstitial sculpture weak aprinum. 



b' secondary and small tertiary riblets inter striatum. 



a'. 17 ribs at apex Letsonae. 



^) *i. Dentaliicm elephantinum Linne. PI. I, fig. i. 



1758. Dcntaliuin clcphantinuvi Linne, Syst. Nat. (10). p. 7S5. 



1766. Dentaliwn elephayitimtjn Linne, Syst. Nat. (12), p. 1263. 



1788. Dentaliuin elepliantinitin Linne. Gmel. Syst. Nat. (13), p. 3736. 



1801. Dentaliuin elephantinum Linne. Lam., Syst. An. s. Vert. p. 326. 



18 18. Dentaliuin elephantinum Linne. Lam., Syst. An. s. Vert. p. 343. 



1818. Dentaliuin elephantinum Linne. WooD, Index Testae, p. 183, N" 2. 



i860. Dentaliuin elephantinum Linne. SOWERBV, Thes. Conch. Ill, p. 102, pi. 223, fig. 4. 



l) Species mavked with an asterisk have not been obtained by the Siboga. 



