210 EOCENE MOLLUSCA. 



(8 — 10) slightly convex; the posterior margins narrow, very slightly depressed, rather 

 thickened at the edges, and presenting round the suture two raised lines, obscurely 

 granulated ; in front of these, two or three fine, thread-like lines run along the middle 

 part of the margin, granulated by the lines of growth, which are much elevated until 

 they cross the shoulder, and give a wrinkled appearance to the margin. The spiral 

 bands over the other parts of the whorls are numerous, irregular, and unequal ; smaller 

 ones alternating with large ones. The aperture is narrow, and of an oblong-oval 

 form ; the outer lip arched, and the sinus, which is moderately wide, and not very 

 deep, is placed in the front part of the margin, immediately behind the shoulder. 



In the ornamentation the present species resembles P. helix, but the narrow posterior 

 margin, the position of the sinus, and the slight but nearly regular convexity of the 

 whorls, giving a symmetrical appearance to the shell, distinguishes it as well from 

 that species as from P. crassa. 



Size. — The largest specimen figured would be, if perfect — axis, nearly 4 inches ; 

 diameter, 1 inch. 



Localities. — Potter's Bar, Chalk Farm, Southampton, Shenfield. 



No. 137. Pleurotoma teretrium. F. E. Edwards. Tab. XXV, fig. 8 a — h. 



P. testa elongatd, fusiformi, spiraliter lineatd : anfractibus convexiusculis, marginibus 



posticis concavis, concentrice lineatis, ad suturam marginatis ; suturis perspicuis ; ultimo 



anfractu valde producto, in canali longo exeunti ; lineis spiralibus irregular ibus, alternatim 



funiculosis et tenuibus, lineis incrementi per-asperatis : aperturd elongato-ovali ; labro valde 



arcuato ; sinu lato, prof undo, in margine collocato. 



Var. nanodis. Testa breviori, latiori ; marginibus posticis anfractuum pauxillum 

 cavatis. 



Var. crebrilinea. Testa minori, graciliori : anfractibus obsolete tuberculatis, lineis 

 spiralibus numerosis, aqualibus, for titer decussatis. 



Var. tuberculata. Testa graciliori : anfractibus sub-angulatis, tuberculatis, ad 

 suturam crenulatis : lineis spiralibus confertis, sub-aqualibus. 



Var. latimarginata. Testa minori: spird tuberculata: marginibus anfractuum 

 latissimis, contra spiram expressis. 



Shell elongate, fusiform, ornamented with numerous spiral, raised lines ; spire 

 elevated, formed of 7 — 9 volutions : whorls somewhat convex, separated by a perspi- 

 cuous suture, and much produced in front, the last whorl terminating in a long, nearly 

 straight canal ; the posterior margins concave, slightly thickened, and occasionally feebly 

 crenulated at the edge. The spiral lines over the middle and front parts of the whorls 

 are irregular, thickish, cord-like bands, alternating with slender, thread-like lines, and 



