M. Deshayes' Monograph of Dentalium. 189 



26. D. BICARINATUM, Desh. D. testa tereti, angustissimd, subrectd, 

 ovato-suhcylindricd, int^s 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 grow^th ; 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 insensibly towards the opening, where they altogether 

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



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



n. Shell cleft at its posterior extremity. 

 A. Ribbed or striated longitudinally. 



27. D. STRIATUM, Lam. D. testd albidd, longitudinaliter costatd, cos- 

 tis crebris, obtusis, subaqualibus ; extremitate posticd profundi fissd. 

 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 ckft, 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 striee 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 ; fissurd posticali profundd, 

 angustd. 



Foss. in Gallia, 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 strise except very distant ones indicative of the groAvth. Apex 



