AEGOCERAS BREVISPINA. 361 



In France it is found at Coiitards, near St. Amand, Cher; at Evrecy and at Curcy, 

 Calvados ; and near Semur, Cote d'Or. In the Middle Lias at Ofterdingen, Germany. 



Aegoceras BREVISPINA, Sowerhy. n. XXXII, figs. 2, 3, 4 ; PI, L, figs. 13, 14. 



Ammonites brevispina, Sowerhy. Min. Conchology, vol. vi, p. 106, tab. 556, 



fig. 1, 1827. 



— NATRix, Zieten. Versteineruiig WUrttembergs, p. 5, tab. iv, 



fig. 4, 1830. 



— — ROTUNDUS, Quenstedt. Ceplialopoden, p. 85, t. iv, fig. 17, 1849. 



— LATiECOSTA, Quenstedt. Ibid., t. iv, fig. 15, 1849. 



— BREVISPINA, d'Orbigny. Pal. Fran9. Terr.; Jurass., t. i, p. 272, 



pi. 79, 1842. 



— — Simpson. Fossils, Yorkshire Lias, p. 69, 1855. 



— — Wright. Quart. Joura. Geol. See, vol. xiv, p. 28, 



1858. 



— — SchVonbach. Eisenstein d. Mittl. Lias ; Zeitschr. 



Deutsch. geolog. Gesellsch., p. 517, 

 Jabr 1863. 



— — Dumortier. Depots Jurass. du Bassin du Rhone, 



vol. iii, p. 97, 1869. 

 Aegoceras BREvisPiNUM, Tate and Bloke. Yorkshire Lias, p. 280, 1876. 



Diagnosis. — Shell discoidal, depressed ; whorls slightly involute, flattened on the 

 sides, and ornamented with blunt, narrow, oblique ribs, on which two small tubercles 

 are developed, one near the spiral suture, and one near the margin of the area, with 

 wide, concave spaces between the ribs ; siphonal area narrow, convex, and crossed by a 

 transverse extension of the ribs between the marginal tubercles ; lobe-line extremely 

 complicated ; aperture oblong, with vertical sides and convex outer surface. 



Dimensions. — Transverse diameter 93 millimetres ; width of the umbilicus 50 milh- 

 metres. 



Description. — This is a very rare Ammonite in the English Lias, and the typo- 

 graphical error in the lettering of Sovverby's plate has created much confusion anent the 

 identification of the shell he called A. brevispina, for the text and the numbering of 

 PI. 556 do not agree. Pig. 1 in Sowerhy 's plate 556 represents Am. brevispina. Sow., 

 and fig. 2 in same plate, Avi. latcecosta, Sow. The numerals have been reversed in error. 



I have had Sovverby's original type specimens redrawn in PI. XXXII of this work in 

 order that the doubt and confusion may be removed. On comparing the type fragments 

 Q,iAe(j. brevispina with Am. natrix, Zieten, from the Middle Lias of Balingen, Swabia, I find 

 them to be identical ; the spines on the ribs nearest the spiral suture are nearly obsolete, 

 and those at the margin are short and well-developed processes, characterised by the 



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