216 



PALEOZOIC TIME LOWER SILURIAN. 



2. European. 



The same subdivisions of the kingdoms of life are represented in Europe as 

 in America, the Radiate and Molluscan having their grander types brought out 

 in species, while the Articulates appear only as Worms and Crustaceans, with 

 Trilobites the predominant tribe. Moreover, the genera of Trilobites, Ortho- 

 cerata, Brachiopods, etc., are, in the main, the same; and many species have 

 been published as identical with American fossils. Among these species of 

 wide range there are the following: — The species Asap>hus giyas, Trinucleus con- 

 centricus, Orthis striatula, Orthis Lynx, Strophomena alternata, Leptsena sericea, 

 Murchisonia bicincta, Bellerophon bilobatus, and others, occurring in the Llan- 

 deilo flags or their equivalents in Great Britain. Trinucleus concentricus is 

 also reported from Bohemia,* Orthis Lynx (or biforata), 0. striatula, Belle- 

 rophon bilobatus, from Russia and Scandinavia. The group of Cystids reached 

 a climax, as in America ; the Bala limestone in Great Britain and equivalent 

 beds in Bohemia and Sweden containing the species in greatest abundance, 

 the number from these regions now known being over forty. 



The annexed cut represents a few of the British species of the Llandeilo flags 

 and Bala limestone. 



Fig. 328, Orthis Flabellulum, one of the coarsely-plaited species of Orthis, an 

 fig. 329, 0. elegantula, both stated to range from the Llandeilo into the Upper 



a^ 



Figs. 328-334. 



Fig. 328, Orthis Flabellulum ; 329, 0. elegantula ; 330, Crania divaricata ; 331, Conocardium 

 dipteruni ; 332, Asaplius Powisii ; 333, Illaenus Davisii ; 334, Ampyx nudus. 



Silurian ; fig. 330, Crania divaricata, the earliest species of the genus, adding 

 another to the number of genera that range from the Lower Silurian to the 

 present time; fig. 331, Conocardium dipterum of the Ayrshire beds; fig. 332, 

 Asaphus Powisii; fig. 333, Tllsenus Davisii Salter; fig. 334, Ampyx nudus, a tri- 

 lobite of the Llandeilo flags; fig. 177" (p. 151), Calymene Blumenbachii, which 

 includes the C. senaria of the Trenton, reported to range from the Bala lime- 

 stone into the Wenlock of the Upper Silurian. 



The earliest Rhizopods (see p. 163) yet discovered have been found by Ehren- 

 berg in the Obolus or Ungulite grit of Russia. The rock is in part a very, soft 

 green-sand ; and the connection of the microscopic Rhizopod shells with the 

 green grains shows, as Ehrenberg states, that it is of the same nature with the 

 vGreen-sand of the Cretaceous. Among these fossils occur the three modern 



