CErHALOPODA. 



197 



Bactrites, Sandberger (=stenoceras, D'Orbigny ?). 



Shell straight ; sutures lobed. 



Type, B. subconicus, Sbger. 



Distribution, 3 species. Devonian, Germany. 



Fig. 61.* 



Ceratites, De Haan. 



Type, C. nodosus (PI. III., Fig. 2). 



Shell discoidal ; sutures lobed, the lobes crenulated (Fig. 61). 



Distribution, 29 species. Devonian — Chalk. Europe, India. 



M. D'Orbigny describes five shells from the gault and Upper 

 greensand as ceratites ; but many ammonites have equally simple 

 sutures, when young. 



Fig. C3.t 



Ammonites, Bruguiere. 



Etymology, ammon, a name of Jupiter, worshipped in Libya 

 under the form of a ram. The ammonite is the cornu ammonis of 

 old authors. 



Synonyms, Orbulites, Lam. Planulites, Montf. 



Shell discoidal ; inner whorls more or less concealed ; septa 

 undulated ; sutures lobed and foliated ; siphuncle dorsal. 



* Fig, 61. Suture of ceratites nodosus (Brug). Tlie arrow in the dorsal lobe points 

 towards the aperture. 



T Fig. 62. Ammonites rnstratus (Sby.) From the U. greensand of Devizes, in the 

 cabinet of W. Cunningtou, Esq. b, front view of one of its partitions. 



