PLEUROTOMARIA. 
295 
cation. The height of the shell and the narrowness of the sinus-band seem 
constant differences in the English specimens from Romer's shell, and therefore 
upon the whole I think that it is safest to regard them as distinct. Other 
differences also probably exist ; for instance the base of the shell seems to be 
decidedly more oblique. 
Affinities. — PI. aspera^ Sowerby/ differs entirely in the character of its orna- 
ment, which is definitely reticulate, and in its convex sinus-band. 
PI. Chudleighensis is distinguished by the fewness and coarseness of its spiral 
lines, the distinctness of its transverse striae, the greater length of the shell, and 
the higher position of the sinus-band. 
PI. rotundata, F. A. Romer,^ appears to differ in being more discoid, and in 
having fewer spiral ridges and more definite transverse striae, which form a 
reticulation with the ridges. 
PI. decussata, var. evexicosta, Sandberger,® which seems to be identical with PL 
imhricata, differs in being a much flatter shell with a broader sinus-band, and more 
decussated and indistinct ridges. 
PI. carinata, Sowerby,* sp., and PI. striata, Sowerby, sp.^ are clearly distinct, 
for they are transversely instead of spirally striated, as also are PI. striata, as given 
by de Koninck,^ and the Canadian PI. Delia, Billings.''' 
The conical specimen in the Museum of Practical Geology mentioned above 
very nearly agrees in contour and other particulars with PI. Lindstromi, 
CEhlert,^ which is evidently very nearly allied. That species may, however, be 
distinguished by its depressed and narrower sinus-band, by the absence of an 
umbilicus, by the riiuch greater indistinctness of the spiral threads, and by the 
clearness of the growth- lines. 
PI. fiUtexta, Hall,^ has a rather lower spire, and is marked by clear transverse 
as well as very fine and numerous spiral lines. 
In PI. Wurmi, F. A. Romer,^" the spiral lines are nodulated by transverse strise. 
1 1840, Sowerby, ' Greol. Trans.,' ser. 2, vol. v, p. 3, pi. liv, fig. 16 ; and 1841, Phillips, ' Pal. Foss.,' 
p. 96, pi. xxxvii, fig. 177 c. 
2 1855, F. A. E5mer., ' Beitr.,' pt. 3, p. 35, pi. vii, figs. 4 «, i and 1884, Clarke, ' Neues Jahrb. 
£. Min.,' Beil.-Band iii, p. 344. 
^ 1853, ' Sandberger,' ' Verst. Ehein. Nassau,' p. 197, pi. xxiv, figs. 4, 4 a. 
* 1813, Sowerby, 'Min. Conch.,' vol. i, p. 34, pi. x, upper and lower figures. 
5 1817, ibid., vol. ii, p. 159, pi. 171, fig. 1. 
•5 1842-4, de Koninck, ' Desc. Anim. Foss.,' p. 399, pi. 31, fig. 2 ; and 1883, de Koninck, Ann. 
Mus. Eoy. H. N. Belg.,' vol. viii, pt. 4, p. 32, pi. xxii, figs. 19—22. 
^ 1874, Billings, ' Palaeozoic Fossils,' vol. ii, pt. 1, p. 61, pi. v, fig. 3. 
8 1887, (Ehlert, ' Bull. Soc. d'Etud. Sci. d' Angers,' p. 28, pi. viii, figs. 6, Ga. 
9 1879, Hall, ' Pal. N. T.,' vol. v, pt. 2, p. 74, pi. xx, figs. 26, 27 ; and pi. xxviii, figs. 15-17. 
10 1843, F. A. Eomer, 'Verst. Harzgeb.,' p. 27, pi. vii, fig. 13 ; and 1884, Clarke, ' Neues Jahrb. 
f. Min.,' Beil.-Band iii, p. 343. 
