190 M. Deshaycs' 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. Ln- 

 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. BREVinssuM, Desh. D. testa tereti, subrectd, postid costatd, 

 antice laevigata; costis tredecim ad sexdecim obtusis, extremitate eminen- 

 tioribns; rimuld angusld abbreviald. 



Foss. in Gallia. 



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

 vnth 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 2^ inches. Diameter of the base 3 lines. 



30. D. SUBSTRIATUM, Desh. D. testd tereti, subrectd, antick Imvi- 

 gatd, postickleviter 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 cxirved, slender, entirely smooth in the two 

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

 fine scarcely prominent striee 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 atiticd lavigatd; fissurd subprO'- 

 fundd, angiistd. 

 Foss, in Gallia, prope Parisios. 



