KONGL. SV. VKT. AlvAUEMIENS HANDL. BAND. 19. N:0 6. 57 



gularly and moderately convex, bein<T most elevated near the medi.-m transverse axis. 

 The apex is close to the anterior margin and only very little prominent. The surface 

 of the shell is covered witli thread iine ornamental lines parallel to the regular con- 

 centric lines of growth, somewhat interrupted by deeper sulci. It is generally even 

 excepting some wavy, irregular, shallow, longitudinal furrows. The aperture is oval 

 with comparatively thin margins, somewhat reflexed outwards. When seen from the 

 side it forms a moderately elevated arch, being highest near the median line of the 

 shell. The central space of the interior surface is surrounded by an oval ring of six 

 pairs of muscular scars, open anteriorly. The posterior ones are narrow and elongate, the 

 middle ones are transversally broad and much enlarged towards the margin of the shell. 

 The surface of these pairs is smooth or only partially scrobiculated. The uppermost 

 pair is more complicated and consists, as in the kindred species, of a more shallow, 

 elongated interior portion, and of a larger exterior one, from the inner corner of which 

 there projects a narrow sinuous groove, directed obliquely upwards and leaving a 

 small, smooth space between itself and the opposite similar one. The lower, interior 

 part of this upper, muscular scar is pearshaped, wide below, with a narroAv, stalklike 

 neck upwards and its surface is finely reticulated by shallow pits and intervening 

 ridges. Some dark, narrow streaks are directed from the enclosed central space of the 

 shell towards the interstices between the muscular scars. The whole central part of 

 the shell inside the scars and to their outer edges is of dark colour, while the outer border 

 is lighter. Near the apex there is on the inside a little oval depression or pit, which 

 quite resembles a scar, filled up, as if there had been a foramen. But I think it is 

 in reality only the mark of the outlines of the initial shell, where now the apex is 

 seen on the outside. The shell is very thin, scarcely exceeding 0,r. millim. in thick- 

 ness and composed of thin, glossy lamellas, which are not perforated by any parasite. 

 The largest specimen has been found at Stor Wede in FoUingbo and has attained a length 

 of 07 millim., breadth of 51 and height of 15 mill. 



This species has nearly the same geographical distribution as the former. It has 

 been found in several specimens in Faro at Lutterhorn, Lansa and Norsholm, in Svarfvare 

 huk, the canal near Westoos in Hall, Westkinde, Hilftingsklint, Lutnmelund, Stor Wede 

 in Follingbo, the limestone cliffs near Wisby and Kyrkberget in Wisby. It has only 

 been found in the strata h and c or the upper and lower limestone and never in thq 

 shale of a. This is rather unexpected as the same species or at least a nearly allied 

 variety, as mentioned above, has been found in the Lower Silurian strata of Esthonia 

 at Borkholm and also in the Upper Silurian at Koik, in the »Jordensche Schicht». These 

 are only a little more elongate and not so enlarged as the specimens from Gotland. In 

 the Lower Silurian of Canada there occui's a Metoptoma Hyrie, of which Billings, Pal. 

 Foss. Canada p. 87, has described a cast which also perhaps on closer examination 

 may be found to be identical. Met.- Erato of the same author, 1. c. p. 39 and Report 

 Progr. Geol. Survey of Canada 1863 p. 145, f. 95, can scarcely, as to outward shape, be 

 distinguished from the Gotland species, only tlic distance from the beak to the margin 

 is longer in the Canadian. 



K. Vot. Akail. Tl.incll. B.imt l!l. N:o ci. 8 



