
OF 
724 STRATIGRAPHICAL GEOLOGY. —[Boox VI. — 
are frequent. The genus Bellerophon is represented by 23 species, 
among which B. Urei and B. decussatus are frequent. The most 
abundant pteropod genus is Conularia (Fig. 339), which often 
attained a length of several inches. ‘The cephalopods number in 
Britain 148 species, belonging among other genera to Orthoceras, — 
Nautilus, Discites, and Goniatites. 
The Crustacea present a facies very distinct from that of the 
\ 

a b 
Fic. 338.—CARBONIFEROUS GASTEROPODS. 
a, Euomphalus pentangulatus (Sow.); b, Pleurotomaria carinata (Sow.), showing 
colour-bands. 
previous Paleozoic formations. ‘Trilobites now almost wholly dis- 
appear, only two or three genera of small forms (Griffithides, 
Phillipsia, Brachymetopus) being left. But other crustacea are 
abundant, especially ostracods (Bairdia, Kirkbya, Leperditia, Bey- 
richia), which crowd many of the shales and sometimes even form 
seams of limestone. A few macrura occur not infrequently, particu- 
larly Anthrapalemon (Fig. 341), Paleocrangon, and Paleo- 
caris, also several phyllopods (Dithyrocaris, Ceratiocaris, 
Estheria, Leaia) with the larger merostomatous Hurypterus 
and the king-crab Prestwichia.1. The Carboniferous Lime- 
stone of the British Isles has supplied somewhere about 
100 genera of fishes, chiefly represented by teeth and 
spines (Psammodus, Cochliodus, Cladodus, Petalodus, Cten-— 
odus, Rhizodus, Ctenoptychius, &c.). Some of these were 
no doubt placoids which lived solely in the sea, but 
many, if not all, of the ganoids probably migrated between 
salt and fresh water; at Jeast their remains are found in 
op oe Scotland in strata full of land-plants, cyprids, and other 
irrrovs Indications of estuarine or fluviatile conditions. : 
Preropop. The second phase of sedimentation, that of the coal- — 
Conularia swamps, is marked by a very characteristic suite of organic 
he ra remains. Most abundant of these are the plants, which 
possess a special interest inasmuch as they form the oldest 
terrestrial flora that has been abundantly preserved. ‘his flora is 


» 

1 Recent researches by Mr. B. N. Peach go to show that the Carboniferous Zury- 
pterus was almost certainly a gigantic arachnid and not a crustacean. Some splendid 
specimens of its scorpion-like combs and feet have been obtained from the Lower Carbon- 
iferous rocks of the South of Scotland. 
