KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:<) 2. 15 



1889. Wachsmuth, C, and Springer, F. »Crotalocrinus: its structure and zoological posi- 

 tion. Loc. cit. Xov. 27th 1888, pp. 364—390, Plates XIX, XX. 



1891. — — »The Perisomie Plates of the Crinoids.» Loc. eit. 1890, pp. 345— 3 9 1', 

 Plates IX, X (pubd. Feb. 1891). 



1882. Trautschold, H. »Ueber Crinoideen, Zusätze und Berichtigungen.» Bull. Soc. Irap. 

 Nat. Mosc. vol. LVII, pp. 140 — 145. Moscow. Contains a note by S. Loven, 

 on Sieyocrinus. 



1886. Carpenter, P. H. »Note on the Structure of Crotalocrinus.» Ann. Mag. Nat. Hist. 

 ser. 5, vol. XVIII, pp. 397 — 406. London. 



1891. Bather, F. A. »British Fossil Crinoids, — V. Botryocrinus, Wenlock Limestone.» 



Ann. Mag. Nat. Hist. ser. 6, vol. VII, pp. 389—413, Plate XIL London, May. 



1892. — — »British Fossil Crinoids, — VIII. Cyathocrinus; C. acinotubus, Ang., and 



C. vallatus, sp. nov., Wenlock Limestone.» Ann. Mag. Nat. Hist. ser. 6, 

 vol. IX, pp. 202—226. Plate XIII. London, Mareh. 



THE STRATIGRAPH1CAL HORIZONS OF THE GOTLAND CRINOIDS. 



In this paper the hörizons at which the various fossils have boen found are signified 

 by the letters c, d, e, f, g, Ii. These letters refer to the divisions of the Silurian rocks 

 of Gotland, as maintained by Prof. G. Lindström in his paper Feber die Schichtenfolge 

 des Silur auf der Insel Gotland» 1 ). These Divisions are as follows: — 



a Oldest red Marl-slates. Probably in situ öff the W. coasl near Wisby, below sea-level. 

 ? feet Characterised by Arachnophyllum diffluens. Only stems of Crinoids recorded. 

 Probably equivalent to the Esthonus-heds of Oesel. 

 b Soft, light-grey Shales. Along the shore N. of Wisby. Characterised by Stricklandinia 



50 feet. Urata. No Crinoids recorded. Correlated with Upper Llandovery. 



c Newer Shales and Sandstone. The Shales underlie the ensuing Limestone in the N. 



from 25 P ar * °^ * ne i s ' :lll( '' being exposed mostly along the W. coast: the Sandstone takes 



to their place in the S. part of the island. In N. blue-grey or greenish härd shale 



feet. w j|]j i' nne stone nodules; near Westergarn and on Stora Carlsö soft, blue laminated 



shale; S. of Klintehamn härd, laminated »Kalkschiefer»; at Fröjel and Eksta soft, 



blue-green niarl; near Petesvik barder, calcareous marl; from Fardhem to Burs 



more sandy; from Grötlingbo to Hoburg sandstone, with a few intercalated 



shale-bands. Coinciding with the petrographic variation are various Faunal 



Districts. Such Echinoderms as occur are found chiefly in the Southern and 



less argillaceous regions. Correlated with the Wenlock Shale, and partly with 



the Beyrichien- and Choneten-Kalk of German authors; probably also with the 



»Thonschiefer mit Graptolithen» of Berendt and Dames; also with Niagara Shale. 



') Neues Jahrb. f. Min. Jahrg. 1888, Kd. I, pp. 147 — 164, Plate V. 



