KONGL. SV. VET. AKADKMIENS IIANDL. BAND. 19. N:0 6. 



87 



outer side is ornamented by longitudinal, elevated bands, of iinequal size, large and 

 narrow, as it were, in pairs with larger interspaces. They are not quite parallel with 

 the median axis and spreading toward the aperture in a sort of pinnate arrangeraont, 

 new ones being intercalated from the dorsal keel. Tliese bands are interrupted by 

 transverse, sinuose, sunk lines, in older and worn specimens much reminding of the 

 fringed sutural lines of the diaphragms of the Aramonites. As seen in figs. 4 and 6 pl. 

 IV these interruptions are very evident along the transverse lines and it is indeed a 

 new set of longitudinal bands whicli starts in the front of such transversals. These 

 are, as raay clearly be seen through fig. 39 pl. III, the edges of the old expanded 

 apertures, which in perfect and intact specimens must have projected as imbricated 

 laraella?, the one beyond the other, as in some of the Cyrtolites. 



Along the median line of the dorsal side an elevated, narrow keel is stretching, 

 corresponding with the groove on the inside; at some distance from the superior margin 

 of the outer lip there is a row of elongated, elliptical apertures with elevated borders. 

 These apertures continue for a while open and become further down on the spire closed 

 with shelly matter as in Haliotis. 



Longitudinal axis of aperture 94 millim., transverse diam. of same 95 millim., 

 diameter of last whorl near the aperture 31 millim. Distance from the edge of the 

 outer lip to the opposite end of the whorl 115 millim. 



This, one of the largest of our Silurian shells, has been found in many places on 

 Gotland. In the oldest shale beds from Halls huk, along the shores north and south 

 of Wisby, in the shale of Djupvik in Eksta, Petesvik in Habblingbo and further inland 

 in the shales of Wisne myr in Fardhem, and also in the sandstone of Bursvik. The 

 superjacent limestone and oolite beds also contain it. It has been found in these 

 beds at the canal near Westöös in Hall, in Martebo, around Wisby, in a section near 

 Stjernarfve in Eksta, in the limestone near Lau church and the oolite of Bursvik. From 

 the upperraost limestone strata it has been obtained at Lutterhorn in Fårö, Martebo, 

 Kålens qvarn near Wisby, the upper limestone of Slite, W^ialrasudd at Fårösund and at 

 Fröjelklint. It occurs almost always in casts, only a few specimens having been found 

 with the shell, which is very thin. 



Among nearly related species Treman, trigonostoma Hall and Wiiiteield Geol. 

 Surv. Ohio, vol. II p. 146, pl. VIII f. 5 resembles Tr. longitudinalis in a high degree. 



2. Tremanotus compressus n. 



Pl. IV iigs. 8 — 12. 



Shell discoid, involute, whorls five, transverse with the lateral diameter largest. 

 In a section the whorls are of an elliptical outline. In the nuclei, which Jiave been 

 found, nothing is left of the expanded aperture. There are faint traces of longitudi- 

 nal lines. The apertures on the dorsal keel are smaller, more regular and closer set 

 than in the preceding species, elliptical or ovate. Largest diameter 34 millim. Breadth 



