320 THE LIAS AMMONITES. 



The varieties of this species figured by d'Orbigny were collected in France from the 

 lowest beds of the Lias with GryphcRa incurva, Sow. ; at Pont-Auber, near Avallon 

 (Yonne), and Champlong, near Semur (Cote-d'Or) : at Jamoigne (Luxembourg) ; and in 

 several places in Germany near Balingen, Degerloch, Echterdingen, Vaihingen, Stuttgart, 

 and other localites. It everywhere characterises beds which are interposed between 

 the Planorbis- and the BucMandi-senes. 



Aegoceras catenatum, Sowerhy. PI. XIX, figs. 5 — 7. 



Ammonites catenatus, Sowerhy. De la Beche, Geological Manual, 3rd ed., 

 p. 334, fig. 74, 1833. 



— TRAPEZOiDALis, Sowerby. Ibid., p. 334, fig. 75. 



— CATENATUS d'Orbigny. Pal. Franf., Terr. Jurass., vol. i, p. 301, 



pi. xciv, 1842. 



Diagnosis. — Shell discoidal, compressed ; whorls depressed, one third involute, and all 

 exposed ; sides flattened, with twenty-eight to thirty strong, simple ribs, which are twice 

 arched, elevated, and enlarged as they approach the outer margin, and interrupted in 

 the siphonal area, which is smooth or crenulated ; aperture oblong, compressed, notched 

 by the preceding whorl. 



Dimensions. — Diameter 53 millimetres ; width of the umbilicus 23 millimetres ; height 

 of the last whorl at aperture 18 millimetres; thickness 13 milHmetres. 



Description. — This rare Ammonite is found in the Lower Lias at Barrow-on-Soar, 

 and is seldom seen in any of the metropolitan Museums. It is a very well marked form, 

 and a fair example of the Angulati group. The species was first found by my old friend 

 the late Sir Henry De la Beche, along with other Lias fossils in limestone at La Spezia, 

 Italy, and is recorded in the following passage: — "As far, therefore, as the evidence of 

 the Ammonites and Orthoceratites extends, we may refer the limestone of La Spezia either 

 to the Lias or the Coal Measures. There will be observed a curious correspondence in 

 the organic character of the rocks of the Savoy and Erench Alps above noticed, and con- 

 sidered as Lias by M. Elie de Beaumont, with that of the limestones of La Spezia. 

 In the former Coal Measure plants are found with Belemnites ; in the latter Coal Measure 

 Ammonites also occur with Belemnites. 



" The organic character of the Oolitic group in the Alps is far from being well ascer- 

 tained, and the undescribed organic remains found in the same series of the South of 

 Erance are exceedingly numerous, so that it may be possible to discover some of the 

 La Spezia Ammonites in both situations ; and the organic remains of the South-east of 

 Erance, the Alps, and La Spezia, may hereafter mutually assist in determining the 

 relative ages of the rocks in which they are discovered." ^ 



1 ' Geol. Manual,' 3rd edition, p. 334, 1833. 



