364 THE LIAS AMMONITES. 



line describes three lobes and three saddles. The siphonal lobe is wider, and as 

 long as the principal lateral ; it is ornamented on each side with four branches, of which 

 the two superior form single points j the third has two, and the fourth four. The 

 siphonal saddle is a little wider than the principal lateral lobe, its space is divided 

 laterally into wide leaves, and terminates in one bi-lobed and two tri-lobed folioles. 

 The principal lateral lobe is outwardly formed of three digitations, and internally of six 

 unequal processes, and terminates in one long digit. The lateral saddle, one third 

 wider than the principal lateral lobe, divides into two nearly equal-sized leaves, each 

 formed of three folioles. The small lower lateral lobe has an irregular figure, one 

 long lateral digit is directed inwards, and there are two small laterals on each side and a 

 long terminal process. The auxiliary saddle, half the size of the lateral, is divided into 

 two portions ; the small auxiliary lobe is oblique, and formed of a single digitation. 



Affinities and Differences. — This shell very much resembles Stephanoceras Blagdeni, 

 Sow., figs. 157, 158, p. 251, from the Inferior Oolite. In the breadth of the whorls 

 it is a very variable species ; the marginal tubercles are also always more or less 

 approximated, and the transverse strise across the siphonal area are not by any means 

 constant as regards number and elevation. It cannot be mistaken for any other shell 

 in the Middle Lias, as its specific characters are so prominent and well developed. 



Locality and Stratigraphical Position. — It has been collected from the Jamesoni beds 

 at Fenny Compton, Warwickshire ; Munger and Paulton, Somerset ; and Robin Hood's 

 Bay, Yorkshire. 



In France it is rare at Coutards pres St. Amand-Montrond, Cher ; Avallon, Yonne. 



In Germany it is found in the Jamesoni-hedi at Ofterdingen and Gammelshausen. 



I have several specimens from the Numismalismergel at Riederich near Metzingen and 

 . One of these is figui-ed PI. LXIX, figs. 5, 6. 



Aegoceras gagatetjm, Young and Bird. PI. XXXVH, fig. 8, 9. 



Ammonites gagateus, Young and Bird. Yorkshire Coast, 2nd ed., p. 255, 



pi. xii, fig. 7, 1828. 

 — Simpson. Monograph on the Ammonites of the York- 

 shire Lias, p. 13, 1843. 

 — — Fossils of the Yorkshire Lias, p. 45, 1855. 



— NEGLECTUs, — Ibid., p. 45, 1855. 



INTEGRIUOSTATUS, — Ibid., p. 46, 1855. 



— CEKcus, — Ibid., p. 47, 1855. 



— ILLATUS, — Ibid., p. 39, 1855. 



Aegocekas GAGATEUM, Tate and Blake. Yorkshire Lias, p. 275, 1876. 



Diagnosis. — Shell discoidal, depressed ; umbilicus wide, whorls round, inner margin 



