No. 3.] HUNT — ON CAMBRIAN AND SILURIAN. 295 



bites ; which was followed, in 1828, by his classic work on the 

 same subject. [Uber de Palaeaden oder so-genanten Tiilobiten, 

 4to. with six plates, Leipsic] In these works were described and 

 figured, among many others, two genera — Olenns, which included 

 Paradoxides, Brongn, and Battus, including Agnosfus of the 

 same author. Meanwhile, Hisinger was carefully studying the 

 strata in which these trilobites were found in Gothland, and in 

 the same year (1828) publi!^hed in his AnfecJcningar, or Notes 

 on the Physical and Geognostical Structure of Norway and 

 Sweden, a colored geological map and section of these rocks as 

 they occur in the county of Skaraborg ; where three small cir- 

 cumscribed areas of nearly horizontal fossiliferous strata are 

 shown to rest upon a floor of old crystalline rocks, in some parts 

 granitic and in others gneissic in character. The section and 

 map, as given by Hisinger, show the succession in the principal 

 area to be as follows, in ascending order : 1. granite or gneiss ; 2. 

 sandstone; 3. alum-slates; 5. orthoceratite-limestones ; 4. clay- 

 slates. By a curious oversight the colors on the legend are 

 wrongly arranged and wrongly numbered, as above ; for in the 

 map and section it is made clear that the succession is that 

 just given, and that the clay-slates (4), instead of being below, are 

 above the orthoceratite-limestones (5). 



In 1837, Hisinger published his great work on the organic 

 remains of Sweden, entitled Lethoex Suecica [4to. with forty-two 

 plates.] Ill this he gives a tabular view, in descending order, of 

 the rock-formations, and of the various genera and species de- 

 scribed. The rocks of the areas just noticed appear in his fourth 

 or lowest division, under the head of Fomiat'tones transltionls, 

 and are divided as follows : 



a. Strata calcarea rcccntiora Gottlandiaj. 



b. Strata schisti argillacci. 



c. Strata schisti aluminaris. 



d. Strata calcarea antiqiiiora. 



e. Strata saxi arenacci. 



The succession thus given was however erroneous, and pro- 

 bably, like the mistake in the legend of the same author's map 

 just mentioned, the result of inadvertence, the true position of 

 the alum-slates (c) being between the older limestone {d) and 

 the basal sandstone (e). This is shewn both by Hisinger's map 

 of 1828, and by the testimony of subsequent observers. In 

 Murchison's work on the Geology of Russia in Europe, publish- 



