10 G. LINDSTRÖM, A SILURIAN CYATHASPIS FROM GOTLAND. 
impressions of paired branchial grooves and with the pineal 
pit environed by two cuneiform impressions on each side, as. 
in the English and Galician species. 
In the Russian island of Oesel some fossil fishes have: 
been found which in the shape and structure of their scales 
come very near to the Gotland form. PANDER's description 
and figures ') of his Tolypelepis nearly coincide with it. His 
figures of the surface (P1. 6, fig. 24 a—b are nearly like it); 
fig. 24 c. represents, although somewhat roughly, the numerous 
small tubuli which lie close under the surface (compare my 
figures 5 & 6, P1. IT) and fig. 24 d gives a view of the prisma 
like vacuoles. On turning to PANDER's descriptions it is evi- 
dent that he intended to describe the same structure as is 
found in my specimens. Lately RoHon ?) has published ex- 
cellent figures of the miecroscopic structure in this genus, to 
which FR. ScHMiDtT has given the new name of Tolypaspis. 
Though having the superficial ridges nearly resembling those 
of Cyath. Schmidtii it, however, in the said structure differs 
much more from this, than does the Oniscoiepis dentata.?) 
But this again is more irregularly built and as to the ridges 
resembles the sections of Pteraspis, although the ridges are 
broader than in the last mentioned genus. 
The geologiecal age, to which this Cyathaspis belongs, 
may be best settled by a review of the organic contents of 
the stratum which enecloses it. This stratum is situated in 
the south eastern parts of Gotland, in the parish of Lau, 
where during the last few years a canal is being cut in or- 
der to drain the marshy grounds on the plateau a little to 
the south-west of the church of Lau. 'The uppermost limestone 
beds which form the hills round the church are rich in fossils 
and, especially, are known to contain the curious operculated 
coral Rhizophyllum gotlandicum and others. These beds are 
denuded towards the south near the small lakes of Lau where 
there is an outcrop of a soft gray, marly shale, forming the 
underbed, as almost everywhere in Gotland. . The fossils con- 
tained in the shale beds are enumerated below. 
Pisces. Cyathaspis? Schmidtii E. GEINItz. 
') Monographie der fossilen Fische des silurischen Systems der Russisch- 
Baltischen Gouvernements, p. 60. | 
”) Die Obersilurischen Fische von Oesel. II Theil. in Mém. Acad. Imp. 
des Sciences de St. Petersbourg, VII:e Série. T. XLI, N:o 5, pl. II, fig. 56. 
SYRGAS pEALIE fr 
