M. Deshayes' Monograph of Detitalium, 187 



19. D. POLITUM, Linn, D. testd tereti, subarcuatd, continud, albiddf 

 politd, striis annularihus confertissimis, 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 striee. Opening 

 oblique, with very thin and sharp margins. 



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



20. D. DuFRESNll, Desh. D. testd tereti, arcuatd, lesvigatd, continud, 

 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 middling, strongly curved, pointed, smooth, perfectly free from strias, 

 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, translucidd, 

 hyalind, glaberrimd, nitidd, subviriduld. 



Habitat ? 



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

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

 and solid. 



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



22. D. LACTEUM, Desh. D. testd tereti, subarcuatd, l(svigalissimd, 

 nitidissimd, albidd, lacted, 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 



