642 



HISTORICAL GEOLOGY. 



1006. 



1007. 



part of the blade, the part that carries, on its under surface, the cells 

 occupied by the animals, as illustrated in Figs. 1007 a and 1007 h. 



Brachiopods were numerous, especialh^ of the 

 gQnexQ. Prodi(,ctus (Fig. 1013), Chonetes (Figs. 1012, 

 1015), S'pirifer (1010, 1014), Athyris, Dielasma 

 and Rhynclionella. There were also species of the 

 Lower Silurian genus Orthis (Fig. 1008), but none 

 of Stropheodonta, Merista, MeristeUa, so well rep- 

 resented in the Devonian. 



4. Mollusks. — Among Mollusks, Lamelli- 

 branchs were common. Under Gastropods, the 

 genus Belleroplion, which first appears in the Cam- 

 brian ; the Lower Silurian genera, Euomphalus, 

 Murchisonia, Pleurotomaria, and the Upper Si- 

 lurian Platyceras, Loxonema, and Macroclieilus, 

 which had many Devonian species, were still well 

 represented. The shells of Platyceras are often 

 attached to a Crinoid, like those of a modern Crepidula to an oyster. 



Cephalopods were of many kinds under the old genus Orthoceras ; and 

 Discites, Goniatites, Gyroceras, had their species. Nautilus (Endolobus of 

 Hyatt) spectahilis M. and W., from the Chester limestone, was two feet in 



Bktozoans. — Figs. 1006, 1007 a, b, 

 Archimedes Wortheni (1007 a and 

 1007 6, xf). Hall. 



1008-1015. 1(112 



Kill ^- v_vVJ 



1012 a 



W' W 



1015 a 



Beachiopods. — 1008, Orthis Michelini var. Biu-lingtonensis ; 1009, Spiriferina spinosa ; 1010, Spirifer increbes- 

 cans ; 1011, Eiimetria Verneuiliana ; 1012, Chonetes Iffinoisensis ; 1013, Productus punctatus ; 1014, Spu-ifer 

 biplicatus ; 1015, 1015 a, Chonetes ornatus. Figs. 1008-1011, HaU ; 1012, Koninck ; 1018, Meek ; 1014, 1015, 

 SwaUow. 



diameter; Orthoceras nobile M. and W., of Illinois, was five to six feet long, 

 and a foot in diameter; and Gyroceras Burlingtonense Owen, five inches in 

 diameter. The species represented in Figs. 1016, 1017 are from the Goniatite 

 bed of Rockford, Ind. 



