PERMIAN PERIOD. 375 



and Germany, characteristic particularly of the Lower Zechstein, and occurring 

 also in the Kupferschiefer ; Strop>halosia excavata, England, Germany (the spe- 

 cies of the genera Productus and Strophalosia are exceedingly abundant in 

 individuals) ; Camarophoria Schlotheimi von Buch, from Russia, Germany, and 

 England (the genus is related to Terebratula and Pentamerus, and is peculiar 

 to the Carboniferous and Permian) ; Camarophoria superstes, Russia. 



(c.) Conchifers. — Monotis speluncaria, England, Russia, and Germany in the 

 Lower Zechstein; Mytilus {31odiola) Pallasi, Russia and Germany; Mytilus 

 squamosum, Russia, England; Avicula Kazanensis, Russia, Germany; Balcewellia 

 antiqua, England, Russia, Germany; Axinus dubius Schlotheim, a very common 

 species in England, Germany, and Russia. (It includes Schizodus Schlotheimii 

 Geinitz, Ax. obscurus Sowerby, and other so-called species.) The genus Axinus 

 is of the same family with Trigonia, a characteristic genus in the Reptilian 

 age. 



(d.) Gasteropoda are rare in the Permian. There are a few species of Murchi- 

 sonia and Straparollus, Palaeozoic genera, besides some others. 



(e.) Ceplialopods existed, and among them two or three species of Ortho- 

 eeras. 



3. Articulates. — No Trilobites are known. Ostracoids are common. The 

 first of the Tetradecap,ods (p. 153) is found in this formation. The only 

 species known is an Amphipod, Prosoponiscus problematicus, from the Permian 

 of Durham, England, first described by Schlotheim, but recently explained by 

 Bates. Decapods of the order of Macroxirans appear to have commenced in the 

 Coal formation. But the first of the Brachyurans is announced from the Per- 

 mian by von Schauroth, who names it Hemitrochiscus paradoxus ; Geinitz regards 

 it as related to the Pinnotheres family, one species of which is the little crab 

 found in the oyster : length about one-eighth of an inch. 



4. Vertebrates. — (a.) Fishes. — Fig. 617, Palseoniscus Freislebeni Agassiz, 

 one-third the natural size. Common in the Kupferschiefer, and also found in the 

 Coal measures in England at Ardwick. Over forty species of fishes have been 



Fig. 617. 



Palseoniscus Freislebeni (X X A)- 



described. The more characteristic genera are Palseoniscus, Platysomus, Acro- 

 lepis, Pygopterus, and Ccelacanthns, but they are also all Carboniferous. 



(b.) Reptiles.— Nine or ten species have been described belonging to the tribes 

 of Labyrinthodonts and Lacertians. Fig. 617 A, Proterosaurus Sjjeneri, regarded 



