ELEMENTS OF GEOLOGY. 
Fig. 481, 
Productus semireticulatus^ Martin, sp. 
(P. antiquatm^ Sow.) Mountain 
Limestone. England, Russia, the 
Andes, etc. 
Fig. 482. 
SjpiTifera trigonalis, Martin, sp. Mount¬ 
ain Limestone. Derbyshire, etc. 
Fig. 483. 
this large number only 40 species are common to the under¬ 
lying Devonian rocks, 9 of them being Cephalopods, Y Gas- 
teropods, and the rest bivalves, chiefly Brachiopoda (or Pab 
liobranchiates). This latter group constitutes the larger part 
of the Carboniferous Mollusca, 157 
species being known in Great Britain 
alone, and it will be found to increase 
in importance in the fauna of the pri¬ 
mary rocks the lower we descend in the 
series. Perhaps the most characteristic 
shells of the formation are large spe¬ 
cies of Productus^ such as P. giganteus^ 
P. hemisphmricus^ P, semiretimlatus 
(Fig. 481), and P, scahriculm. Large 
plaited spirifers, as Spirifera striata^ S, rotundata and S, tri¬ 
gonalis (Fig. 482), also abound; and smooth species, such as 
Spirifera glabra (Fig. 483), with its numerous varieties. 
Spirifera glabra, Martin, sp, 
Mountain Limestone. 
Fig. 484. 
Terebratulahastata, Sow., 
with radiating bands of 
color. Mountain Lime¬ 
stone. Derbyshire, Ire¬ 
land, Russia, etc. 
Fig. 485. 
Aviculopecten sublobatus, 
Phill. Mountain Lime¬ 
stone. Derbyshire, 
Yorkshire. 
Fig. 486, 
Pleurotomaria carinata, 
Sow. (P. fiammigera, 
Phillips). Mountain 
Limestone. Derby¬ 
shire, etc. 
Among the brachiopoda, Terehratula hastata (Fig. 484) de¬ 
serves mention, not only for its wide range, but because it 
often retains the pattern of the original colored stripes 
