Dentalium. 



ANNELIDA. 



243 



Family II.— MALDANIiE. 

 Branchiae of the animal intermediate; tube open at both ends. 



Gexhs III.— dentalium.— LJnnffiw. 



Shell tubular, open at both ends, arcuated, increasing in 

 diameter towards the anterior extremity, where the aperture is 

 large and round ; opening of the pointed end very small, and 

 with a lateral fissure in some species ; external surface ribbed, 

 striated, or smooth. 



1 . Dentalium NiTENs. — The Shining DeuUilium, pi. XC VIII. 

 fig. 63. 



D. nitens. Sowerby, I. p. 159, pi. 70, figs. 1, i. 



Almost straight, gradually tapering to the smaller end, which 

 is somewhat thickened ; opening at the point, circular ; aper- 

 ture expanded ; surface even and shining. 



In the London Clay, Highgate. 



2. Dentalium acuminatum. — The Pointed Dentalium, pi. 

 XCVIII. fig. 74. 



D. entails. Sowerby, I. p. 159, pi. 70, fig. 3. 



Slightly arcuated, nearly smooth, with the lines of growth 

 on the surface a little waved ; opening of smaller end, smooth ; 

 the aperture acute in the edge. 



The London Clay, Hordwell Cliff, &c. 



3. Dentalium striatum. — The Striated Dentalium, pi. 

 XCVIII. fig. 09. 



D. striatum. Sowerby, I. p. 100, pi. 70, fig. 4. 



Surface with ten or eleven very regular, longitudinal, acute, 

 prominent striae, which are most elevated at the smaller end 

 of the shell, giving it a triangular appearance ; between each 

 of the laiger striae are from one to four very minute interven- 

 ing ones, which are most conspicuous towards the middle of 

 the shell, with numerous fine lines of growth ; apertui-e circular; 

 length, about two inches. 



The Loudon Clay, Barton. 



4. Dentalium decussatum. — The Decussated Dentalium, 

 pi. XCVIII. fig. 59. 



D. decussatum. Sowerby, I. p. 101, pi. 70, fig. 5. 



Surface with upwards of twenty longitudinal striae, and 

 several obscure intervening ones, with numerous distinct 

 oblique lines of growth ; aperture elliptical ; diameter of the 

 shell nearly double that of D. striatum. 



Chalk JIari, Xewtimber, Sussex ; the Oault, Westerham, 

 and llidge, Sussex. 



5. Dentalium ellipticuu.— The Elliptical Dentalium, pi. 

 XCVIII. fig. 63. 



D. ellijiticum. Sowerby, I. p. 101, pi. I'K figs. 0, 7. 

 Nearly straight, abruptly tapering, and somewhat compressed ; 

 sui-Jace rather uneven, covered with rough lines of growth ; 



aperture circular, witli the extenial edge elliptical ; diameter 

 of aperture nearly half an inch in some specimens. 

 The Gault, Folkestone, and Greensand, Blackdowu. 



6. Dentalium costatum. — The Ribbed Dentalium, pi. 

 XCVIII. fig. 73. 



D. costatum. Sowerby, I. p. l()i>, pi. 70, fig. 8. 



Surface with from twelve to fifteen close set ribs, the fur- 

 rows being about equid in width ; crossed by obscure lines of 

 growth ; aperture circular. 



The Red Crag, Holywell, and Coridline Crag, Sutton. 



7. Dentalium planum. — The Plain Dentalium, pi. XCVIII. 

 fig. 72. 



D. planum. Sowerby, I. p. 179, pi. 79, fig. 1. 



Gradually tapering, and gently curving ; surface smooth ; 

 aperture circular, with the lip a little thickened, and sharp at 

 the edge ; small end rather acute ; length about an inch. 



The London Clay, Bognor, Reading, &c. 



8. Dentalium cylindeicum.— The Cylindrical Dentalium, 

 pi. XCVIII. fig. 71. 



D. cylindricum. Sowerby, p. 179, pi. 79, fig. 2. 



Nearly straight, hardly tapering, the smaller end being 

 nearly as wide as the other ; cylindrical, smooth ; aperture 

 circular. 



The Greensand, E.xmouth, Devon. 



9. Dentalium incrassatom. — The Thickened DentaUum, 

 pi. XCVIII. fig. 70. 



D. incrassatum. Sowerby, I. p. 180, pi. 79, figs. 3, 4. 

 Greatly tapered, cm-ved, swelling near the aperture, which 

 is circular, with a sharp lip ; surface smooth. 

 The London Clay, Highgate. 



10. Dent.-u.ium medium. — The Middle-sized DentaUum, 

 pi. XCVIII. fig. 65. 



D. medium. Sowerby, I. p. 181, pi. 79, fiir. 5. 



Gradually tapering, somewhat trumpet-shaped internally ; 

 aperture circular, wide, lip sharp, and becoming suddenly 

 small ; external surface covered with transverse striae, or con- 

 spicuous lines of growth ; substJince of the shell thin. 



Lower Greensand, Blackdown. 



11. Dentalium anceps. — The Obscure Dentahum, pi. 

 XCVIII. fiig. 7. 



D. anceps. Sowerby, Geo. Tr. 2ud Ser. V. p. 136, pi. 8, 

 fig. 17. 



Slightly arcuated ; longitudinally ribbed for a third of its 

 length from the apex ; one rib on each side being prominent 

 and sharp ; the lower portion smooth ; aperture round. 



The London Clay, Harapstead. 



12. Dlntalium ent.\le. — The Eutalis Dentalium, pi. 

 XCVIII. fig. 64. 



D. entule. Deshayes, Mon. pi. 15, fig. 7. 



Slender, smooth, glossy, and somewhat arcuated, tapering to 

 a small per\iou3 iwint, sometimes with a few transverse 

 wrinkles. 



