KONGL. ,SV. VET. AKADEIIIENS IIANDLINGAH. BANlJ. 19. N:0 6. 139 



not haniionizu with tliut of the palsDOzoic Euomphali. As Stoliczka has sliown'), 

 most of the Jurassic forms belong to the genus Discohelix, of which there probably 

 already is a representative in the Devonian strata of Nassau^). It is possible that this 

 genus has continued during the Tertiary times and still survives in the Mediterranean 

 and Atlantic seas. 



As to the species here described in tliis genus, E. tuba n. may be only provisio- 

 nally included in it, as it deviates somewhat in its form and possibly rather is an 

 Oriostoma. On the other hand, it nmst by future researches be decided whether Orio- 

 stoma angulatum Wahlenbebg rather not is an Euomphalus. 



1. Euomplialus Gotlandicus n, 



PI. XIII tig. 19—31. 



Shell disciform, involute or disjointed, at the highest with live whorls. These 

 are cylindrical and nearly triangular in section, the slit and its concomitant ridge being 

 on the apical side. The oldest mutation or variety, which occurs in the shale beds, 

 has only the nucleus left and is generally involute (figs. 19 — 22) with a wide and open 

 umbilicus showing all whorls. The aperture is in the best specimens triangular, the 

 ridge forming an angle, the outer lip thin, a little reflexed outwards. The tendency to 

 disjoint can be traced in specimens where the whorls are coiled in, but have some free 

 space between them, to those where they are quite uncoiled as in figs. 23 — 25. From 

 the same geological horizon the specimens figured in figs 30 — 31 have also been ob- 

 tained. In the uppermost limestone strata near Wisby hitherto only uncoiled speci- 

 mens have been found as shown in figures 26 — 29. In them the aperture is more 

 triangular than in the involute forms from Wisby a. The ornamentation of the sur- 

 face is nearly alike in all, consisting of thin, transverse threads bent in an angular 

 line curved backwards from the apertural slit. This slit is situated nearly in the 

 middle of the lower edge of the aperture and forms a highly obtuse angle. The three 

 oldest whorls are filled with solid calcareous deposit, figs. 22, 29, and the uppermost 

 surface of this stratum is deeply concave. 



H. 20 mill., br. 42 mill, of involute specimen. 



H. 15 mill., br. 39 mill, of uncoiled specimen. 



The involute variety is found in great numbers in the lowest shale near Wisby, 

 and also at Westergarn and Stormyr in Rute. The uncoiled variety is found in the 

 same localities and moreover in the uppermost limestone beds of Kyrkberget in Wisby 

 and at Killens Qvarn, Hogran, the shore of Slite, Weskinde. 



From the shale of Wisby some nuclei have been obtained in all particulars re- 

 sembling the common involute one, excepting in having some slight longitudinal ridges 

 along the apical side. They are, however, not in a sufliciently good state of preserva- 

 tion for description and delineation. 



') Uastropodcn tier Hierlatz Schichten. Sitzuugsbeiichteu der Ak. Wiss. VVieu, Bd 43, 1, p. IbO. 

 *) Euomphalus rota Sandb. Nassau p. 212, pi. 26 f. 5. 



