KONOL. SV. VET. AKADEMIENS HANDL. HANI). 19. N:0 6. 87 



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

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

 the median ;ixis and spreading toward the aperture in a sort of pinnate arrangement, 

 new ones being intercalated from the dorsal keel. These 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 Ammonites. As seen in figs. 4 and 6 pi. 

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

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

 are, as may clearly be seen through fig. 39 pi. Ill, the edges of the old expanded 

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

 lamella?, 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 mj-r in Fardhera, 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 Westoos 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 uppermost limestone strata it has been obtained at Lutterliorn in Faro, Martebo, 

 Kiilens qvarn near Wisby, the upper limestone of Slite, Wialmsudd at Farosund and at 

 FrOjelklint. 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 WniTFiELO Geol. 

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



2. Tremanotus compressus n. 



PI. IV figs. 8 — 12. 



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

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

 found, nothing is left of the expanded aperture. Tiu-re arc faint traces of longitudi- 

 nal lines. Th(! apertures on the dorsal keel are smaller, tnore regidar and closer set 

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



