L10CERAS OPAL1NUM. 35 



specimen, though slightly different from either, seems to be to a certain extent 

 intermediate in character, and its true position is not easy to determine. It is 

 figured in the hope that more specimens may be collected. 



Liooeras opalinum (Reinecke). Plate XIII, figs. 1 — 10. 



1818. Nautilus opalinus, Reinecke. Maris Protog., p. 55, figs. 1, 2. 

 1830. ? Ammonites pbimobdialis, Zieten. Verstein. Wiirtt., pi. iv, fig. 4. 1 

 1849. — opalinus, Quenstedt. Die Ceph., pi. vii, fig. 10. 



1867. Leiocebas opalinum, Hyatt. Bulletin Mus. Comp. Zool., vol. i, No. 5. 



p. 101. 

 ? 1874. Ammonites concavus, Durnortier. Etudes pal. Bassin du Rhone iv, 



pi. xiii, figs. 1, 2, 3. 



1874. — opalinus, Durnortier. Ibid., pi. xlix, figs. 14, 15, 16. 



1878. Ludwigia opalina, Bayle. Explic. carte geol. France, pi. lxxx, figs. 1, 



5,6. 



1884. Haepoceeas opalinum, Wright. Lias Amm, Pal. Soc, pi. lxxx, figs. 6 — 8 



(not 5, but perhaps 3). 



1885. — E. Haug. Beitr. Monog. Harpoceras, Neues Jahr- 



buch, Beil.-Bd. iii, p. 681. 



1886. — Vacek. Oolithe Cap San Vigilio, Abh. der k. k. 



geol. Reichsanstalt, Bd. xii, No. 3, pi. vi, 

 figs. 4 and 11 only. 

 1886. — elegans, Vacek (non Sowerby, non Young and Bird). Ibid., 



pi. vii, fig. 17 only. 

 1886. Ammonites opalinus, Quenstedt. Amm.Schwabischen Jura, pi. Iv, figs. 1, 



2, 3, 10, 12, 18 only, 22 ?, but cer- 

 tainly not 9, 13, 16, 20, 21, &c. 



1875. Non Ammonites opalinus, Lepsius. Beitrage Juraf. Unter-Elsass, pi. ii, 



figs. 4, 5, which I believe to be 

 another very different species. 



Discoidal, compressed, subcarinate, whorls slightly convex, with a very small 

 depression in the inner area, ornamented with numerous very fine sigmoidal strise, 

 which have a strong forward sweep on the ventral area. The ventral area in the 

 young state slopes acutely, and possesses a small sharp carina. As the shell 

 increases, the latter gradually lessens, and the ventral area becomes less and less 

 acute, until at last on the body-chamber of the adult the ventral area is actually 

 rounded (PI. XIII, fig. 2). The inner margin is slightly concave, rather upright in 

 the type-form except on the body-chamber. The inclusion is, as usual, slightly less 



1 This figure shows a much wider umbilicus, and the striae very straight. It is evidently not 

 typical, and may not be a synonym of Lion, opalinum. 



