DEVONIAN ANIMALS 



333 



brachiopods and lamellibranchs, and a few univalves. It is worthy of 

 remark that many of these univalves are fresh-water species. 



Cephalopods. — The characteristic Palaeozoic Cephalopods, or Ortho- 

 ceratites, continue, but in greatly-diminished numbers and size ; but the 



Fig. 415. Fig. 418. Fig- 417. 



Figs. 411-418.— Devonian Lamellibranchs and Gasteropods: 411. Conocardium trigonale (after 

 Logan). 412. Aviculopecten parilis (after Meek). 413. Ctenopistha antiqua (after Meek). 414. 

 Lucina Ohioensis (after Meek). 415. Spirorbis omphalodes. enlarged. 416. Spirorbis Arkanen- 

 Bis. 417. Orthonenia Newberryi (after Meek). 418. Bellerophon Xewberryi (after Meek). 



Goniatites, a coiled-chambered shell, which seems to be the beginning 

 of the Ammonite family, are introduced first here. This family, as 

 already explained, is distinguished by 

 the complexity of the junction of the 

 septa and the shell (suture), and by 

 the dorsal position of the siphuncle. 

 In the Goniatites the sutures are not 

 yet very complex. They are only 

 zigzag. This is shown in the fig- 

 ure. 



Crustacea. — The very characteris- 

 tic Palaeozoic order Trilobites is still 

 abundantly represented, although it 

 has already passed its prime, and is 

 diminishing in number and size of 

 species. The Euryptends introduced 

 in the Upper Silurian maintain their place through the Devonian. 



Fig. 419. 



-Goniatites lamellosus (after 

 Pictet). 



