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 Pmtremites, a kind that was particularly abundant in the 

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



Figs. 496-497. 



Fig. 498. 



Oonchifers. — Fig. 498, 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 

 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. 

 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- 



Platyceras dumosum. 



