240 EOCENE MOLLUSCA. 



No. 161. Pleurotoma desmia, F. E. Edwards. Tab. XXVII, fig. 5. 



P. testa elongatd, fusiformi, tuberculatd, spiraliter fasciolatd et lineatd: spird sub- 

 conicd, valde productd : anfractibus convexis, sub-angulatis, longitudinaliter plicatis ; mar- 

 ginibus posticis depressis, concavis, concentrice lineatis, ad suturam cingulo duplici, 

 distanter plicato, cinctis ; ultimo anfractu repente coarctato, incanali breviculo exeunti : 

 fasciolis nicmerosis, antice simplicibus, ceteris inaqualibus, nonnullis majoribus, crasse 

 granulatis, cum aliis minoribus simplicibus, alternantibus : aperturd ovali ; labro valde 

 arcuato, intus plicato ; sinu lato, sub-trigono, in margine collocato. 



Shell elongated, fusiform, tuberculated, and ornamented with concentric bands 

 and raised lines ; the spire rather thick, nearly conical and much elevated, almost 

 equalling two thirds of the whole shell in length : the whorls short, convex, and 

 obscurely angulated at the shoulders, where they present a double row of small, 

 transverse tubercles j the posterior margins much depressed, hollowed out, and con- 

 centrically lined along the middle, and bordered round the suture by a double line, 

 distantly and obliquely plicated by the lines of growth of the sinus, which are very 

 prominent over the whole width of the margin ; the last whorl is suddenly contracted 

 in front, and terminates in a rather short and narrow canal, widely notched at the 

 anterior extremity. The spiral bands over the middle and front parts of the whorls 

 are divided with much regularity into rows of coarse, oblong granulations, placed 

 nearly below each other in an oblique direction, following the curve of the outer lip, 

 and giving an appearance of plication to the whorl : the rows of granulations, which 

 are separated by thickish, raised lines, rounded on the surface, diminish in size towards 

 the front part of the whorls, until, on reaching the canal, they barely exceed the 

 intervening lines in size, and the granulations become nearly obliterated. The 

 aperture is of an oval form ; the outer lip much arched, projecting in front, and pli- 

 cated within ; and the sinus, which is placed rather towards the front of the margin, 

 is wide, moderately deep, and sub-trigonal in form. The columella is slightly curved, 

 and presents in front, at the anterior extremity, a conspicuous crest or comb. 



The present species, in the young state, somewhat resembles P. microdonta, but 

 the shell is narrower, the spire relatively longer, and the canal shorter ; the regular 

 granulations which characterise the concentric ornamentation also render it easily 

 separable. It is apparently confined to the middle eocene formations of Barton, where 

 it is not uncommon. 



Size.— Axis, 1 inch and 8-l2ths, nearly ; diameter, half an inch. 



