BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND. 7. N:0 5. 19 



surface is convex. The leagth in clifFercnt examples varies 

 between 0,8 1 mm. and 1,3 mm., and tlie widtli between 0,4 5 

 and 0,6 7. The examples are abundant, but they are all left 

 forms. These jaws appear to correspond with the large dental 

 plate (Zahnstuckc) of the existing genus Arabella. The simi- 

 lar! ty is very close to the type speciraens from the English 

 Wenlock and Liidlow. 



Locality. Wisby and Fröjel, 



Arabellites arcuatus, IIinde. Plate 2 figs. 52, 52a. 



1879. Arabellites sinulis var. arcuatus. Hinde. Quart. Jour. Gcol. 

 Soc. Vol. 35 p. 385. Pl. 20 fig. 20. 



Jaw crescentiform, the upper surface slightly concave; an 

 oblique pointcd shank extends to below the middle of the 

 plate ; the lower portion of the exteriör lateral margin is 

 slightly curved and with a linear ridge, the front portion of 

 the free lateral margin is arehed inwards; there is a single 

 prominent conical tooth which is preceded by two minute den- 

 ticles and followed by a series of 8 to 10 conical pointed re- 

 curved ones. The under surface has an elongated curved 

 aperture similar to that of the preceding form, in front of this, 

 the surface is convex. Length 0,5 8 mm. by 0,2 9 mm. in width- 

 This form is very rare; it agrees closely with the type, from 

 the Devonian of Canada, but it is much smaller. 



Locality. Wisby. 



Arabellites angustus, n. Plate 2 fig. 53. 



Jaw narrow, elongate; the upper surface nearly flat; the 

 anterior margin thickened, incurved, and prolonged down- 

 wards into a short blunted shank; below this, the margin is 

 curved to the obtuse posterior extremity. In front is a stout 

 conical tooth, succeeded by two minute denticles, then follows 

 a second prominent tooth, below which, to the posterior ex- 

 tremity the slightly curved margin has 10 closely set minute 

 conical denticles. The under surface has a narrow aperture 

 extendinor from the lower end as far as the shank. Length 

 0,63 mm., width 0,31 mm. This jaw is of the same character 

 as the preceding, but it is much narrower, and the shank is 

 shorter. 



Locality. Wisby. 



