192 M. Deshayes' Monograph of Dentalium. 



very acute, very deeply cleft, sometimes to one-third of the whole length 

 of the shell. Cleft capillary, scarcely visible to the naked eye. The 

 variety is slenderer, its rings are narrower, and much more numerous, and 

 its cleft rather deeper. 



Length 2 inches 2 lines. Diameter of the base 2 lines ; in the variety 

 barely l^ line. 



34. D. FissuRA, Lam. (haudSowerby.) D. testd tereti, subarcuatcty 

 angustd, subulatd, l(jevissimd,fissurd tenuissimd, dorsali, posticd. 

 Habitat in mari Indico .!" — Foss. in Gallia, apud Grignon, &c. 



Size middling. Shell throughout smooth, shining, slightly curved, 

 very acute, slender, subtransparent, without any appearance of striae of 

 growth. Cleft median dorsal, deep and narrow. Opening small, rather 

 oblique, very thin and fragile. 



Length 1 inch 3 lines. Diameter of the base 1^ line. 



35. D. ACUMINATUM, Desh. D. testd tereti, minutd, subrectd, acutis- 

 simd, IcEvigatd ; fissurd capillari, profundd. 



Foss. in Gallia, prope Parisios. 



Shell small, very smooth, shining, pointed posteriorly like a needle. 

 Base broader in proportion than in the larger species. Apex very slen- 

 der. Cleft median dorsal, deep, but very narrow and capillary, invisible 

 to the naked eye. 



Length 7 lines. Diameter of the base f of a line. 



36. D. NEBULOSUM, Linn..'' D. testd albidd, Icevissimd, subarcuatd ; 

 extremitate posticd maculatd, viriduld, subtilissime striata; maculis 

 albidis, opacioribus; fissurd posticd later ali. 



Habitat in mari Indico } 



Shell milk-white, subdiaphanous, slightly curved, smooth, shining ; 

 apex marked with exceedingly fine striae, visible only under a powerful 

 magnifier. Colour of the apex usually light yellowish or greenish, 

 marked with dull-white, more or less regular, zig-zag spots, which become 

 larger, and are insensibly lost towards the middle, or on the anterior half 

 of the shell. Opening not very large, with very thin and cutting edges. 

 Cleft on the right side ; the shell being in this respect intermediate be- 



