106 (!. LIND.STUOM, ON THE SILURIAN (iASTUOlMjDA AND TTKHOlMlDA OF (iOTLAND. 



tite limestone of Dalecarlia and Oland. It has almost the same general form as the 

 Gotlaiulie one, the ornamentation is (juite the same, the slit band is different by the 

 longitudinal ridge, tliough still above the median line of the band, being placed nc^arer 

 to it than in any other of the later mutations, where it is placed higher. In the speci- 

 men from Wisby (fig. 10) the ridge is placed at the highest and in the next from 

 Ostergarn it is midway between the position in the two former. There are, of course, 

 in this, as in almost all other species of shells individual variations as to the greater 

 or smaller convexity of the whorls, the size of the apical angle, of very little im- 

 portance as to the specific distinction. Thus I think that PI. subconica Kjerulf may 

 without hesitation be jjlaced in this species. It is not at all identical with PI. sub- 

 conica Hall, as this author expressly states, that it is "cancellated", whereas the 

 Norwegian shell only is transversally striated. Murchisonia Hercynias Billings, Pala^oz. 

 Foss. Canada p. 158 f. 141, comes also near to PI. elliptica, but is more elongated, 

 with more acute apical angle, and may possibly be only a variety of this. PI. elliptica 

 GoLDFUSS Petrif. Germ. p. 50, pi. 178 fig. 4, is not at all related to our species. It is 

 a sinistral and longitudinally carinated, Devonian species, only found as nucleus. De 

 KoNiNCK led by the general, exterior shape thinks, in his Faune Carbonif. de Belgique 

 II pt. 3, p. i)4 that »Trochus ellipticus Hisingeid) ought "probablement" to be placed 

 in his genus Flemingia, but this cannot be so, since the slit band has been demon- 

 strated in this species. 



In some specimens, as that from Wisby and that figured by Ferd. Roemer from 

 the Lower Silurian, there is the peculiarity, that the impression of the slit band on 

 the nucleus is a shallow groove, while it in all other specimens is a distinct keel or 

 at least not so much grooved. The geological range of this species in Sweden is then, 

 according to the statements, given above, from the Upper Gray Orthoceratite limestone 

 included, through the Chasmops limestone into the Upper Silurian shale beds of 

 Gotland. 



19. Pleurotomaria bicincta Hall. 



PI. VIII tig. 15—25. 



f Pletirotomnrin mu/ulatn 1838 Sow. in Sil. Syst., 641 pi. 21 f. 20 (not identipjil with PI. aiis;iilata M.\c Cov 



Sil. Foss. Ireland, 16, pi. I f. 17). 

 Murchisonia bicincta ') 1847 Hall Pal. N. York vol. I, 177 pi. 38 tig. 5 a— h. 



1850 Salteii Geol. Survey of Canada, Organic Rem., Dec. I, 19, pi. IV f. 5 — 6. 

 Turbo .tj). )jprol)nl)ly ncw» 1851 Salter Q,u. Journ. Geol. Soc. vol. VIII, 178, pi. IX f. 15. 

 Pleur-otomaria sj). 1S58 Fr. Schmidt E.stland, 202. 



/Pleurotomaria Intifasciata 1862 Mac Coy Synops. Silur. Foss. of Ireland, 15, tab. I f. IG. 

 rnW/o?imn(Eimeina)/r(<«((1868 Hall 20;tli Rep. N. York State Cab., 345, pi. 15 f. 7— 8. Revised. Ed. 394, tab 



15, fig. 7—8. 

 Trochonema rectilatera 1872 Hall & Whitfield 24;tli Rep. N. York State Cab., 193, ligund in llie, 27:tli 



Rept. pi. 13 f. 4—5. 



Shell conical, turbinated with five or six whorls. Each whorl is moderately con- 

 vex and shows, when free, three different faces, the inferior one, sloping against tlic 



') Murchisonia bicincta? Meek iV Worthek Geol. Illinois vol. HI, 317 pi. 3 f. 4 is too obscure to be 

 with any certainty regarded as this species. 



