106 o. LINDSTRÖM, ON TIIE SILURIAN OASTROPODA AND PTEROPODA OF GOTLAND. 



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

 Gotlandie one, the ornamentation is quite the same, the slit band is different by the 

 longitudinal ridge, thougli still abovc the median line of the band, being placed nearcr 

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

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

 Ostergarii 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 Pl. subconica Kjerulf may 

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

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

 Norwegian shell only is transversally striated. Murchisonia Hercyniaa Billings, PaUtoz. 

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

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

 Goldfuss Petrif. Germ. p. 50, pl. 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, exteriör shape thinks, in his Faune Carbonif. de Belgique 

 II pt. 3, p. 94 that »Trochus ellipticus Hlsinger» 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. 



Pl. VIII fig. 15-25. 



? Pleurotomaria nngulata 1838 Sow. in Sil. S\'st., 641 pl. 21 f. 20 (not identical with Pl. angulata Mac C'oy 



Sil. Foss. Ireiand, 16, pl. I f. 17). 

 Murchisonia bicincia ') 1847 Hall Pal. N. York vol. I, 177 pl. 38 fig. 5 a— h. 



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

 Turbo sp. »probably new» 1851 Salteii Qu. Journ. Geol. Soc. vol. VIII, 178, pl. IX f. 15. 

 Pleurotomaria sp. 1858 Fe. Schmidt Estland, 202. 



? Pleurotomaria latifasciata 1862 Mac Coy Synops. Silur. Foss. of Ireiand, 15, tab. I f. 16. 

 Trochonema(Eunema)fatua 1868 Hall 20:tli Rep. N. York State Cab., 345, pl. 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, figured in the 27:th 



Rept. pl. 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 the 



') Murchisonia bicincta ? Meek & VVouthen Geol. Illinois vol. III, 317 pl. 3 f. 4 is too obscure to be 

 with any certainty regarded as this species. 



