260 



PALEOZOIC TIME. 



represented in Fig. 492. Though ovoidal in form, it is related to the 



Figs. 493-495. 

 495 



Brachiopods. — Figs. 493, 494, Spirifer acuminatus ; 495, Sp. gregarius 



pentagonal Pentremites, a kind that was particularly abundant in the 

 Lower Carboniferous (Fig. 580, p. 298). 



Figs. 496-497. 



Conchifers. — Fig. 493, Lucina(?) proavia ; 497, Conocardium trigonale. 



Brachiopods were very numerous ; and figures 493 to 495 repre- 

 sent common species. The genus Productus here had its first species 



— a genus that was very numerously 

 Fig. 498. represented in the Carboniferous 



formation. Its earliest species are 

 half an inch broad, and some of the 

 later three or four inches. The char- 

 acter of the shell is illustrated in 

 Figs. 238, 239, a, page 173. 



There were also various other kinds 

 of Mollusks. Among them occur spi- 

 nous species of the genus Platyceras*, 

 one of which is represented in Fig. 

 Piatyceras dumosum. 498. In the hornstone was found (by 



Dr. White) the dental apparatus of a 

 Gasteropod, represented in Fig. 484 A o. [p is another form, in horn- 



