17 LiGNiTic Stage 17 



Pleuroloma langdoni, PI. 2, fig. 6. 



Syii. PI. acii If! I ua /a fHeWprin, Proc. Acad. Nat. Sci. Phila., uSSo, p. 374, 

 pi. 20, fig. 10. 



P/. lajigdoiii Aid., Bull. Am. Pal., vol. i, p. 60, pi. 4, fig. 5. 

 PL sp. f Har., Bull. Am. Pal., vol. i, p. 192, pi. 17, fig. 14. 



Aldricli' s description. — (See vol. 1, p. 6c.) 



We have already seen how in the Midway stage (vol. i, p. 

 192) the forerunner of this species differs from the lyignitic or 

 typical form by its less elevated spire, fewer and more prominent 

 costse, greater basal deflecftion of columella, etc., and we might 

 addlhat the subsutural band, of but slight elevation in either 

 form, is traversed \>y a spiral line in the Midway form while it is 

 rendered crenulate in the lyignitic by the greater strength 

 of the lines of growth as they approach the suture. 



A small specimen in my own colledlion from Bell's landing, 

 has more nearly the ribbing of the Lignitic form though the 

 subsutural elevation is simple like the Midway specimen. 



The Hatchetigbee specimens are remarkable for the great 

 comparative size of the body whorl, short spire, fine and oblique 

 costation, coarse spiral and lines of growth, and coarse beading 

 of the subsutural elevated band. In these too it is especially 

 noticeable that it is the lower margin of the subsutural band 

 that is most strongly beaded. 



The origin of this species and that of P. nasuta is clearly in 

 the Midway P. persa\ for among the numerous Gregg's landing 

 specimens there are P. nasiita extremly close to P. persa and at 

 Bell's there are .specimens of nasuta on the high road to lang- 

 doni. 



Lignitic localities. — Ala.: Bell's landing; Woods bluff , Hatche- 

 tigbee bluff. 

 7)y!>(?.— Aldrich's colle(5tion, from Hatchetigbee. 

 Specimen Jigured . — Woods bluff. 



Pleurotoma roscoei, n. sp., PI. 2, fig. 7. 



Specific chara5lerizatio7i. — Whorls 8 to 10, smooth, the upper 

 whorls very small, while the body whorl and one or two above 

 are comparatively large, giving the sides of the spire a concave 

 appearance; two .spiral lines just beneath the suture on the last 



