Coal-measure Fossils. 131 



numerous, and comprise 18 genera and 160 species, the 

 most strikingly characteristic of which are Productus, 

 Spirifera, Rhynchonella, and Terebratula. The genus 

 Orthis only yields 12 species, a great decrease when com- 

 pared with its development in Silurian seas. There are 

 334 species belonging to 49 genera of Lamellibranchiata, 

 which, unlike their comparative development in Silurian 

 rocks, far exceed the Brachiopoda, both specifically and 

 generically, indicating a remarkable approach to the types 

 of Secondary times, in which Lamellibranchiate molluscs 

 by far predominate. The most common of these are 

 Aviculopecten, Posidonomya, Area, Conocardium, 

 Edmondia, Modiola, Nucula, and Sanguinolites. 

 Of Gasteropoda, there are 29 genera and 206 species, 

 among which are many species of Euomphalus and 

 Pleurotomaria. Of the Nucleobranchiata, 23 species of 

 Bellerophon are known, and 148 species of Cephalopoda, 

 the chief of which are Ooniatites, Nautilus, and 

 Orthoceras. Ninety-nine genera and 221 species of 

 fish have been described, some of which probably lived 

 alike in the sea and in fresh and brackish water. 



In the Carboniferous rocks, chiefly in the Coal- 

 measures, more than 500 species of fossil plants have 

 been named, a large proportion of which are ferns, 

 some of great size. The most common genera are Sphe- 

 nopteris, Pecopteris, Neuropteris, Cyclopteris, Odon- 

 topteris, Caulopteris (tree-fern), &c. The remaining 

 plants belong chiefly to genera of Calamites (Equisitee 

 of large size), Lepidodendron (tree Lycopodiums), 

 and Sigillaria, Fig. 29. Coniferous trees, the fruit of 

 which is Trigonocarpum, also occur. In the Coal- 

 measure strata of Britain there have also been found 

 many fresh-water Crustacea of the genus Cypris, fresh- 

 water bivalves, Anihracomya, Anthracosia, &c., wings 



