M. Deshayes' Monograph of Bentalium, 187 



19. D. POLiTUM, Linn. D. testd tereti, subarcuatd, continud, albidd, 

 politdf striis annularihus confertissvmis, tenuissimis. 



Habitat in mari Indico. 



A large and beautiful species, rather strongly curved, pointed, polished, 

 shining, subdiaphanous, milk-white. Very numerous transverse strise, 

 scarcely visible to the naked eye, cover the whole of the shell, from the 

 base to the apex ; they are not placed at regular distances, and some of 

 them are coarser than the others, shewing that they depend on the growth. 

 Apex very acute, constantly destitute of longitudinal striae. Opening 

 oblique, with very thin and sharp margins. 



Length 2 inches 8 lines. Diameter of the base 3 lines. 



20. D. DuFRESNii, Desh. D. testd tereti, arcuatd, IcBvigatd, continudf 

 acuminatd, 



Foss. in Burgundia. 



Regarded by Lamarck as the analogue of his D. nigrum^ which is to 

 be rejected from the genus as being probably the case of some larva. 

 Size middhng, strongly curved, pointed, smooth, perfectly free from striae, 

 whether longitudinal or transverse ; narrow. Base not large ; opening 

 perfectly circular, with the margin thin and sharp. 



Length 10 lines. Diameter of the base 1 line. 



21. D. TRANSLUCIDUM, Desh. D. testd tereti, subrectd, transluciddf 

 hyalindf glaherrimd, nitidd, suhviriduld. 



Habitat -? 



Size middhng. Shining, transparent, greenish yellow, perfectly free 

 from strise. It is neither elastic, flexible, nor corneous, but is calcareous 

 and sohd. 



Length 1 inch. Diameter of the base rather more than 1 line. 



22. D. LACTEUM, Desh. D. testd tereti, suharcuatd, IcBvigatissimd, 

 nitidissimd, albidd, looted, subtranslucidd. 



Habitat in mari Indico. 



Smooth like D. Entalis, but smaller and narrower, and invariably 

 milk-white and subtransparent. Shell thin, never exhibiting any appear- 

 ance of striae at its apex. 



n2 



