THE DEVONIAN PERIOD 



459 



B 



c^mp ■ ■ i\\ D e 



Fig. 432. — Devonian pelecypods : A, Pterinea flabellum ; B, Modiomorpha concen- 

 tric a; C y Conocardium ohioense ; D, Buchiola retro striata; E, Palceoneilo constricta. 



Cephalopods. — A rather incon- 

 spicuous member of this class, the 

 goniatite (Greek, gonia, angle), but 

 one whose modified descendants were 

 to become the most prominent inver- 

 tebrates of the Mesozoic, began in 

 the Devonian. The important char- 

 acteristic of this coiled cephalopod 

 was the angled and lobed suture line 

 (Fig. 434 A, B), i.e., instead of smooth 

 partitions (septa, p. 434) which joined 

 the outer shell in straight lines or in 

 simple curves, the septa were crumpled 

 at the edges at the juncture with the outer shell 



Fig. 433. — Devonian gastropods: 

 A, Stropho stylus expansus ; B, Platy- 

 ceras dumosum: C, Loxonema noe. 



forming angled 



v 5 



A - 



X *■ 



Fig. 434. — Devonian cephalopods : A, M antic oc eras oxy; B, Tornoceras mithras. 



