KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 19. N:0 6. 43 



opening between them. The shell is exceedingly thin and coiisequently wrinkled and 

 inucli cnished, but still retaining the delicate details of its fine ornamentation. It 

 consists of two layers, the inner one being thinner and of a paler colour, The colour 

 is påle yellow and in some instances brownish. The transverse ridges of crenulations 

 which adorn the exteriör surface are tive on a length of 2 millimeters, and bent in an 

 obtuse angle upwards, towards the median axis of the side, in some the inclination 

 being so feeble, that the ridge nearly has the form of a straight line. The longitudi- 

 nal axis is not always exactly in the midst of the side, being in some specimens si- 

 tuated a little nearer the outer edge and thus dividing the face in two unequal moie- 

 ties. The furrows between these ridges are nearly twice as large as them. The orna- 

 mentation of the ridges and the furrows varies with the distance from the apex. Near 

 this the ridges are smooth withoiit any indentations, but they are higher up first beaded 

 by blunt tubercles, which from the middle of the shell take the shape of more or 

 less blunt spines, as is shown on a magnified scale in figures 1 — 3. Each spine con- 

 tinues downward into the furrows in a sort of handlelike prolongation, obliquely slan- 

 ting towards the median axis of the side and between these handles there are oval, 

 excavated pits. The spines of the adjacent ridges, as seen in figures 1 — 2, are arran- 

 ged in alternating position; every second row having its spines above each other and 

 placed opposite to the interstices of the two nearest, below and above. In a longi- 

 tudinal section therefore, as figure 3, there are seen alternating long and short spiny 

 projections, the long ones being real spines, the shorter again the next ridge, cut 

 through in a spöt between two of its spines. The spines are interiorly hollow towards 

 their base and consequently, when the point is broken off, as often happens, an an- 

 nular opening is formed. The septum, which is situated near the deciduous apex and 

 closes the shell, when the apex is gone, is smooth and glossy, of the same påle yellow 

 colour as the shell and covered by a few irregularly concentric lines. 



Dimensions. Height 44 millim., breadth of a face near the aperture 16 millira.; 

 fragment of another face 23 millim. 



Occurrence. It has been found in the oldest shale beds (a) in Fårö at Kyrkviken, 

 and other localities, in the lowest beds at Hallshuk, on the shore south of Gnisvärd, 

 and at Djupvik in Eksta. It has also been collected in the overlying limestone of Länsa 

 in Fårö, Snäckgärdet and Vattenfallet near Wisby. It is most common in Fårö, from 

 where the State Museum possesses nearly 30 specimens. 



This species has a wide distribution in time and space. I cannot distinguish the 

 specimens occurring in the Upper gray Orthoceratite limestone of Öland, in the Chas- 

 mops limestone and in the Retiolites shale at Borenshult from the Upper Silurian spe- 

 cies ^). There are only small variations depending on the state of preservation and 

 others of mere subordinary value. Nor can I find any specific distinction between the 

 English and Bohemian specimens, which I have seen, and the Swedish ones. The beau- 

 tiful plates of Barrande moreover are decisive. It is unaccountable how this spe- 

 cies has been so often named as C. Sowerbyi De France. In vain I have searched in 



^) For an elucidation of the various groups of the Swedish Silurian formation, mentioued here and elsevvhere 

 in this memoir, see Appendix A. 



