GASTEROPODA. 55 



volution, and the lip curves elegantly from the sinus. The only diiference I can observe 

 in the shells from the two different formations is in the arrangement of the transverse 

 striae, which are broader and more regular in the Crag shell than they are upon the 

 Barton shells, but living under altered conditions would in all probability modify 

 these appearances. 



5. Pleurotoma porrecta. S. Wood. Tab. VII, fig. 1, a — d. 



Pleurotosia porrecta. S. Wood. Catalogue 1842. 



PL Testa porrecta, eloni/ato-fusiformi ; spird turritd, apice acuta ; anfractibus 9 — 10, 

 parum convexis, subangulatis, transversim tenuissime striatis; in medio nodidosis ; canali 

 lonffuisculd recta. 



Shell elongato-fusiform, with an elevated spire and acute apex; volutions 9 — 10, 

 slightly convex, finely striated transversely, and furnished in the middle of each whorl 

 with one row of obtuse, ovate nodules ; aperture ovate ; canal elongated. 



Axis, 1| of an inch. 



Locality. Cor. Crag, Gedgrave. 



When my Catalogue was drawn up I possessed but one mutilated specimen of this 

 species. I have, however, obtained another since that time, and with three more 

 belonging to H. Daniel, Esq. I am enabled to define its characters. The length of the 

 aperture, including the canal, exceeds two fifths of the entire length of the shell, but 

 in many species that character is liable to great variation, and is not much to be 

 depended upon. The nodules are obtuse, oblique, and placed in the centre of the whorls; 

 they are produced by the reflected edge of the lower part of the sinus in the outer lip, 

 which being thickened externally at different periods, leaves permanent nodules which 

 ornament the exterior. They are about ten in the penultimate whorl, but become 

 nearly obsolete on the older part of the shell. It is covered with veiy fine impressed 

 striae, the spaces between them being broad, flat, smooth, and glossy, differing in that 

 respect from the rough, elevated striae upon PI. nodularia, Desh. (Coq. foss. de Par. 

 p. 493, t. 66, f. 23—25). In other respects it much resembles that shell. It misht 

 perhaps be considered as PJ. nodidiferum, Phil. (En. Moll. Sic. vol. ii, p. 1 73, t. 26, f. 1 6), 

 only that he has described that shell as " laevissima," and his figure does not appear 

 quite so tapering as the one from the Crag, and it has also a shorter canal. When, 

 hereafter, the shells are compared, they may prove the same, but not knowing the 

 Sicilian species I have left the Crag shell with its pro\dsional name. A shell in 

 Mr. Lyell's cabinet from Touraine is probably identical with the Crag specimens. 



6. Pleurotoma nodulosa (?). Desh. 



Pleurotoma nodulosa (?). Besh. Coq. foss. des Env. de Paris, pi. 65, fig. 1 1-14. 



A few fragments resembling this Eocene species are in my cabinet, but they are too 

 imperfect for figuring or fair description. My best specimens appear to have had seven 

 convex volutions, covered with obtuse nodules, about a dozen in each volution, with 



