278 THE LIAS AMMONITES. 



M. Bruguiere. In 1830, Zieten figured as A. multicostata a good type specimen from 

 the Lias Limestone of Altingen, near Tuttlingen, so that Bruguiere's specific name was 

 nearly forgotten, when Prof. A. d'Orbigny, in his ' Paleontologie Erancaise,' in 1844, gave 

 an excellent historical account of the species ; this author, however, confused A. Buck- 

 landi, Sow., with A. bisulcatus, Brug., an error which I have endeavoured to rectify in my 

 description of these two forms. 



Arietites rotiformis, Soiverby. (PI. V, figs. 1 — 4 ; PI. VII, fig. 1 ; PI. IX, figs. 1 — 3.) 



Ammonites rotiformis, Sowerby. Mineral Conch., vol. v, p. 76, tab. 453, 1824. 



— oblique-costatds, Zieten. Die Verst. Wiirt., p. 20, t. xv, fig. 1, 1830. 

 rotiformis, von Buch. tfber ammoniten, p. 10, 1832. 



— — Zieten. Ibid., p. 35, tab. xxv, fig. 1, 1830. 



— — d'Orbigny. Paleontologie Francaise, Ter. Jurassique, 



torn, i, p. 293, pi. lxxxix, 1842. 



— — Quenstedt. Cephalopoden, p. 78, 1846. 



— oblique-costatus, Von Hauer, Jahrbuch geologischen Reichsanstalt, 



bd. vi, p. 736, 1853. 



— kotiformis, Studer. Geologie der Scbweiz, bd. ii, p. 30, 1853. 



— — Von Hauer. Die Cephalopoden aus dem Lias der 



Nordb'st. Alpen, p, 13, tab. 1, figs. 1, 2, 5, 1856. 



— — Quenstedt. Der Jura, p. 67, tab. vii, fig. 1, 1858. 



— — Oppel. Die Juraformation, p. 77, 1856. 



— — Dumortier. Depots Jurass. du Basin du Rhone, p. 22, 



1867. 

 Arietites — Tate Sf Blake. Yorkshire Lias, p. 286, 1876. 



Diagnosis. — Shell discoidal, compressed ; siphonal area tricarinated ; whorls numerous, 

 quadrate, slightly involute, and strongly costated ; ribs from twenty-seven to thirty in 

 a whorl, simple, strong, arched, and terminating near the areal angle in a large, round, 

 obtuse tubercle ; siphonal area large and flat, with a median keel, two lateral sulci, 

 and marginal carinas ; aperture quadrate, depressed, sinuous anteriorly. 



Dimensions. — Transverse diameter of specimen figured on PI. IX 175 millimetres; 

 height of aperture 45 millimetres ; width of aperture 40 millimetres. M. d'Orbigny's 

 specimen : width of the last whorl -n^; portion overlapped of last whorl xou > thickness 

 of last whorl ^ % ; width of the umbilicus -^ - of the diameter of the shell. 



Description. — Shell discoidal, compressed, with quadrate whorls, strongly ribbed, 

 and slightly involute. In the specimen I have figured (PI. V, fig. 1) the inner whorls 

 are partly absent, and in part concealed ; in Sowerby's type only four whorls can be 

 counted, the central ones being absent ; in d'Orbigny's fine specimen, which is almost 

 perfect, there are eight whorls, and this we may regard as the normal number in a shell 

 ISO millimetres in diameter; the number of ribs in a whorl differ much in different 



