190 M. Deshayes* Monograph of Dentalium. 



not very acute, but rather more so than in the preceding species ; having 

 a deep median dorsal cleft, which is narrow, and of an equal breadth 

 throughout. In some specimens of this and the other species an appen- 

 dix to the posterior opening is seen similar to that noticed under D. ii w- 

 talis, but in these it is cleft above in the same manner as the shell itself. 

 Opening rather oblique, with very thin and sharp edges. 

 Length 4 inches 4 lines. Diameter of the base 5 lines. 



29. D. BREViFissuM, Desh. D. testd tereti, subrectd, postice costatd, 

 antick IcBvigatd; costis tredeoim ad sexdecim obtusis, extremitate eminent 

 tioribus; rimuld angustd abbreviatd. 



Fos&. in Gallia. 



Large, very little curved, rather broad at the base: apex rather pointed, 

 with from thirteen to sixteen prominent ribs, which become insensibly 

 broader and flatter, disappearing altogether in the anterior part of the 

 shell; the ribs are smooth, rounded, and obtuse. Transverse striae of 

 growth very fine, scarcely visible to the naked eye, scattered irregularly, 

 but becoming much more numerous towards the opening as the ribs 

 vanish. Cleft dorsal, very short and narrow. 



Length 2 inches 4 lines to 2J inches. Diameter of the base 3 lines. 



30. D. SUBSTRIATUM, Desh. D. testd tereti, subrectd, antich Icevv- 

 gatd, postice kviter striatd ; striis minutissimis ; rimd abbreviatd, sub- 

 angustd. 



D. Fissura. Sowerby, Genera of Shells, No. XV, /. 3, 4. ^ 



Foss. in Gallia, prope Parisios. 



Shell large, very slightly curved, slender, entirely smooth in the two 

 anterior thirds of its surface, the remaining portion being occupied by 

 fine scarcely prominent strise varying in number and in length. Cleft 

 median dorsal, broader and rather deeper than in the preceding species. 



Length from 3 inches 2 lines, to 3 inches 4 lines. Diameter of the 

 base upwards of 3 lines. 



31. ,D. SEMi-STRiATUM, Desh, D. testd tereti subarcuatd, extre- 

 mitate posticd recurvd, striatd; parte ardicd lavigatd; fissura subpro- 

 fundd, angustd. 



Foss. in Gallia, prope Parisios. 



