M. Deshayes' Monograph of Dentalium. 189 



26. D. BiCARiNATUM, Desh. D. testd tereti, angustissimd, subrectd, 

 ovato-subcylindricd, intHts duabus carinis oppositis instructd. 



Foss. in Gallia. 



A most singular species. Small, very slender, almost as large at the 

 apex as at the base ; curvature scarcely any. Shell smooth, shining, 

 slightly marked by the strise of growth ; not rounded, but oval : furnished 

 in the interior with two opposite keels, corresponding with the flattening 

 of the sides ; these keels are most prominent near the posterior extre- 

 mity, and diminish insen,sibly towards the opening, where they altogether 

 disappear. Opening oval, oblique, very thin, with the margin sharp. 



Length 8 lines. Longest diameter at the base J a line. 



IL Shell cleft at its posterior extremity. 

 A. Ribbed or striated longitudinally. 



27. D. STRIATUM, Lam. D. testd albidd, longitudinaliter costatd, coS" 

 tis crebris, obtusis, subcsqualibus ; extremitate posticd profundi jissd. 

 Habitat . 



Shell large, white, nearly straight, with from twelve to fourteen round- 

 ed ribs, continued from the apex to the base ; between each of these is a 

 smaller one, or a slightly prominent stria. Apex rather pointed, having 

 on its median and dorsal part a broad and deep cleft, which is broader 

 anteriorly than behind, its edges being cut obliquely inwards. Open- 

 ing large, rather oblique, its margin being by no means sharp. A few 

 transverse strise of growth. 



Length 2 inches 10 lines. Diameter of the base more than 2 lines. 



28. D. GRANDE, Desh. D. testd magnd, tereti, subarcuatd, striatd; 

 striis numerosissimis, confertis, tenuibus ; fismrd posticali profundd, 

 angustd. 



Foss. in GalHa, apud Grignon, &c. 



The largest species knovm. Shell very slightly curved, entirely co- 

 vered with fine and numerous striae, which become flattened towards the 

 opening, where they are always less prominent than at the apex ; no 

 transverse striae except very distant ones indicative of the growth. Apex 



