M. Barrande on the Silurian St/stem of Bohemia. 113 



ness of the Crustaceans. Among the Mollusca, a few rare 

 fragments of Orthoceratites, from the quartzites of the 

 Drabow mountains, mark the first appearance of the Cepha- 

 lapods ; and with them are associated the Pteropods, in 

 several species of Conularia^ soon followed by the Pugiun- 

 culus in the black schist. The same quartzites present the 

 first traces of the Heteropods in some forms of Bellerophon, 

 and also of the Acephalse, in a few species of Avicula and 

 Nucula, whilst the Gasteropods appear in the micaceous 

 slates in the Pleurotomaria, and other forms analogous to 

 the Holopea of Hall. The Brachiopods are represented in 

 each of the fossiliferous bands by peculiar species of Or this, 

 whilst, in the micaceous slates, the genera Orbicula, Lingula, 

 Spirifer, Leptcena, and Terebratula also appear. The great 

 class of the Echinoderms is represented by some considerable 

 traces of Crinoids, by the Cystideae, forming almost entire 

 beds, one or two metres thick, in some localities near the 

 middle of the micaceous slates, and, in the same formation, 

 by some very rare Asteriades, together with a body very 

 analogous to that which Professor E. Forbes has recently 

 described as the Protaster Sedgwickii, The Agelacrinites 

 dates from the Drabow quartzites. Polyparise are extremely 

 rare in this stage, the Calamopora fibrosa being the first that 

 occurs in the micaceous slates, followed, but only in the 

 calcareous nodules, by Calam. Gothlandica, In the same de- 

 posits Graptolites also appear, but have never been observed 

 lower. On the whole, with the exception of the Trilobites 

 and Cystideae, which seem to have swarmed at several 

 epochs, all the other classes of animal life were but feebly 

 represented in those seas. The vegetable kingdom, too, is 

 only indicated by very indistinct traces of Fucoids in all the 

 formations of this stage. 



These facts show that life was now more abundant than 

 in the lower stage. The Trilobites shew this very remark- 

 ably. In C, 7 genera with 25 species were known ; in D, 

 there are 19 genera with 49 species, or 12 genera and 24 

 species more in the upper than the lower group. Nine of 

 the genera, including Asaphus and Trinucleus, are peculiar 

 to it and unknown above, and Agnostus also becomes extinct, 



VOL. L. NO. XCIX.— JANUARY 1851. H 



