LUDWIGIA MURCHISONCE. 17 



from among which he subsequently 1 chose L. Murchisonce to be the type of his 

 genus. Unfortunately, however, his figure of L. Murchisonce ' Explic. Carte geol. 

 France,' plate lxxxv, fig. 1, cannot possibly be considered as a typical specimen 

 of Sowerby's species. It is a variation, and a well-marked variation. I have 

 carefully examined Sowerby's type specimen of L. Murchisonce, which is in the 

 Natural History Museum of South Kensington, and compared it with specimens of 

 my own, which I have taken there. Bayle's figure shows a much more finely ribbed 

 specimen with smaller umbilicus, and is a sufficiently distinct variation to require 

 a name. It is too, unfortunately, the variety of L. Murchisonce that most nearly 

 connects that species with the genus Lioceras. Further particulars I shall give 

 under the description of Ludtvigia Murchisonce. It only remains for me now 

 to say that to retain the generic name Ludwigia for a class of species having 

 in common characteristics different from any others, I think it necessary to 

 slightly amend Bayle's genus making the type of Sowerby's species the type 

 of the genus. I paid another visit to the South Kensington Museum on 

 purpose to examine the suture line of Sowerby's original specimen of 

 L. Murchisonce, and I found it to possess a more rudimentary accessory lobe 

 dividing the siphonal saddle, and a rather thinner and longer superior lateral lobe 

 than the specimen figured by Bayle, besides the other differences mentioned 

 above. As these features are characteristic of the genus, I am anxious to amend 

 Bayle's genus in the way I have stated. 



Ludwigia Murchisonce (Sowerby). Plates I; II, figs. 1 — 5 ; III, figs. 1 — 3. 



1829 Ammonites Murchisonce, Soiv. Mm. Conch, pi. 550. 



1830 — — Zieten. Verstein. Wurttern., pi. 6, fig. 4 only. 



1845 — d'Orb. Ter. Juras., pi. 120, fig. 3 only. 

 1856 — Oppel. Juraformation, p. 368, No. 18. 



1881 Haepocebas — S. Buck. Quart. Journ. Geol. Soc, vol. xxxvii, 



p. 603. 

 1885 Hildoceeas — Haug. Neues Jahrbuch fiir Mineral., p. 686. 



Ludwigia Murchison^!, var. obtusa (Quenstedt). Plate III, figs. 4, 5. 



1830 Ammonites Muechison^e, Zieten. Verstein. "Wurtteinb., pi. 6, figs. 2 a — e. 



1846 — — OBTDSUS, Quenstedt. Ceph., pi. 7, fig. 12. 

 1858 — — — Quenstedt. Jura, pi. 46, fig. 5 only. 



1884 Ludwigia Haugi, Douville. Bull. Soc. geol. France, ser. 3, vol. xiii, p. 26. 



1885 Hildoceeas Muechisonjs and Haugi. Saug. Neues Jahrbuch fiir Mineral., 



Beil.-Band. iii, p. 686. 



1 ' Bulletin Societe geologique de France,' ser. iii, p. 91, vol. vii, January, 1879. 



3 



