KONGL. SV. VE'l'. AKADEMIENS IIANDL. BAND. 19. N:0 6. 113 



Divisio V. INCIS^. 

 25. Pleurotomaria lalbrosa J. Hall. 



Pl. IX figs. 30—38. 



Pleurot. labrosa 1859. J. Hali, Pal. N. York vol. III, 339, pl. 66 f. 1—5, pl. C7 f. 6. 



Pleurot. balteata 1867. Lindström (not Phillips) Nomina foss. Gotl., 23. 



Pleurot. labrosa var. occidens 1868. J. Hall 20:tli Rep. N. York St. Cab. l:st Ed. 343. 



Pleurot. occidens 1868. Hall 20:th Rep. l:st Ed. 364, pl. 15 (6) fig. 11—12. 



1868. Id. 20:th Rep. Revised Ed., 392, pl. XV f. 11—12, pl. XXV f. 9—10. 



1875. Hall & Whitfield Geol. Survey of Ohio, vol. II, 142, pl. 8 f. 2. 



1877. Oeijlert Bull. Soc. Geol, 585, pl. IX f. 6, 6 a. 



1877. Miller American Possils, 160. 



Shell turbinated, with a short spire and the body whorl enlarged rnany tiraes 

 the size of the other whorls. Whorls tive, almost flat or horizontal beneath the largc 

 and prominent slit band, above it convex and ventricose. This band is situated beneath 

 the median line of the whorls, it is obliqne with the surface directed downwards; the 

 thin and sharp edges (fig. 35) transform it into a deep groove, soraewhat wavy in its 

 course (fig. 33). The crescents (fig. 34) are thin, deeply incised lamelliB, concentrically 

 striated, obliquely hiding behind each other. The inferior, flat side of the whorls is 

 transversally striated by crowded lines of growth, which are crossed by a several ele- 

 vated, longitudinal strite in some specimens, while they are completely vvanting in 

 others. The superior moiety of the whorls is ornamented by a niimber of spiral ribs, 

 which together with the longitudinal lines form a regular, cancellated trellis work. 

 There are also finer transverse stria?. The slit in the aperture continues open for a 

 long distance. The aperture is rather rhoraboidal and angidar in the four corners, 

 below, above and at the sides, in the lowest corner acuminate. The exteriör lip is 

 thin and sharp, the interiör or columellar börder thick, smooth and callons, folded 

 back tightly against the body whorl, so that no umbilicus is visible. Height 48 

 millira., breadth 45 mill., longitudinal diameter of the aperture 85 mill., transverse 

 diam. 30 mill. 



It occurs in the soft shale at Wisby, at Westergarn, where the most numerous 

 specimens have been found, Stora Carlsö, Ejmunds, in the canal between Atlingbo 

 church and Hogrän, Klints in Boge and Länsa in Färö. It does not occur in the lime- 

 stone beds above the shale. 



This species is interesting in consequence of its being one of the few which 

 continue in the Devonian formation. It was first described by Hall from that forma- 

 tion and Oehlert låter also found it in the oldcst Devonian strata of the north of 

 France. Its geographical range is also great, as it has been found in England, besides 

 in N. America and France. In England it has been found in the Wenlock Strata at 

 Walsall according to a specimen in the Museum of Practical Geology in London, of 



K. Sv. Vet. Akad lUaiW. Btl. 19. N:o 6. 15 



