J. Starkie Gardner — On the Gault Aporrhdidce. 199 



occurs in all the beds of the Gault; also at Lyme Eegis and Cambridge; 

 on the Continent it is found in the Paris and Mediterranean basins, 

 Switzerland, and at most places where the Gault occurs. Specimens 

 with exaggerated varices are met with at St. Florentin. 



History. — It was named B. marginala by Sowerby in 1836, who 

 figured a fragment of the spire in the Geol. Trans, vol. iv. pi. 11, fig. 

 18, pp. 114 and 365, from the Gault of Kent. His description is, 

 however, not clear, and applies equally to A. carinata. The figure 

 is drawn from a specimen which has the shell partly preserved in 

 the spire, but only the cast of the body-whorl remains ; in conse- 

 quence of this, and of the want of clearness in the engraving, the 

 second anterior keel scarcely shows. As a result, .and from no 

 mention being made in the description of the two keels, all 

 Continental and most English writers, supposing Sowerby's form to 

 have but one keel, re-named the species A. Orbignyana, which 

 really is invariably bicarinated. In the same year, 1836, Michelin, 

 in the Mem. Soc. Geol. t. iii. p. 100, quoted Sowerby's description, 

 but named the shell B. costata. In 1838 B'Archiac included B. 

 marginata in his lists from Novion and St. -Pot ; and in 1842 

 Leymerie notices it from Ervy. Again, in 1842, D'Orbigny figured 

 it as B. Parhinsoni (not of Mantell) in the Terr. Cret., adding a 

 variety of localities to those previously known. In 1850 he entered 

 it in the Prodrome, both as B. costata and as B. submarginata. In 

 1849 we find this shell named B. carinella (not D'Orb.) by Pictet 

 and Eoux, who figured it from the Gault of Saxonnet, etc. ; but in 

 1853 they re-named it B. Orbignyana, a name by which it has since 

 been generally known. It has been cited under various names, 

 generally as B. costata, by many authors. In 1857 by D' Archaic 

 from the Pas-de-Calais; in 1853 by Studer from Ste.-Croix; in 1854 

 by Eenevier from the Perte-du-Ehone ; in 1854 by Cotteau, and in 

 1857 by Eaulin and Leymerie, from the Yonne ; and in 1857 by 

 Ebray from Cosne. In Morris's Catalogue, 1854, it is called mar- 

 ginata. From 1859 it has been known exclusively to European 

 authors under its specific name of Orbignyana ; see Desor and 

 Gressly, Pictet and Campiche, Gabb, Jaccard, etc. In 1864 Pictet 

 and Campiche described a variety as A. obtusa, but it is possible that 

 their specimens may have been casts of A. marginata ; whilst perhaps 

 some of the more elongated casts, they thought to be of Orbignyana, 

 are A. carinata, a species otherwise absent in Switzerland. In 1865 

 Mr. E. Tate described this and marginata as separate species, failing 

 to see that they were identical. 1 ' 



Pictet and Campiche adopted Sowerby's name marginata, and ap- 

 plied it to a species with a single keel on the body-whorl, a form 

 which their fig. 2, pi. xciv., shows to be identical with A. maxima of 

 Price. Their statement, that they " possess specimens from Folke- 

 stone which prove the identity of this type with ours," is difficult to 

 reconcile with their figures and descriptions ; it is, however, abso- 

 lutely certain that Sowerby's marginata is identical with Orbignyana 

 of Pictet and Boux. 



1 Geol. and Nat. Hist. Repertory, 1865. 



