﻿240 INFERIOR OOLITE AMxVIONITES. 



Dumortieria pseudoradiosa (Branco). Plate XLI, figs. 1 — 3, 9, 10. 



1879. Habpocebas pseudobadiosum, Branco. Unt. Dogger; Abb. geol. Spez.- 



Karte Elsass-Lothringen, Bd. 

 ii, pi. ii, fig. 1 only. 

 1881. Ammonites Moorei, J. Buckman. Terminations Inf. Ool. Aram. ; Quart. 



Journ. Geol. Soc, vol. xxxvii, p. 65, 

 fig. 7. 

 1885. — undulatus, Quenstedt. Amm. Schwabischeu Jura, pi. liv, fig. 26. 



1887. Dumortieria pseudoradiosa, Haug. " Polymorpbidae ;" Neues Jahrbucb 



fur Mineral., &c, Bd. ii, p. 141. 



Discoidal, compressed, carinate. Whorls with sides somewhat flattened, 

 ornamented with well-marked, somewhat distant, direct, ventrally-inclined ribs. 

 Ventral area rather broad, fairly defined, ornamented by a small, distinct carina. 

 Inner margin smooth, convex, fairly defined. Inclusion about one-third. Umbi- 

 licus deep in the centre, but more open and flat towards the outside. Termina- 

 tion a plain sigmoidal bend, with a rounded ventral process. 



Branco observed that Dumortier's figures of Am. radiosus did not agree with 

 Seebach's; and he consequently figured three specimens under the name "H. 

 pseudoradiosum" quoting Dumortier's figures as synonyms. I cannot, however, 

 allow that Branco's specimens agree with Dumortier's figures ; for, excepting fig. 3, 

 they have fewer and broader whorls, greater inclusion, and coarser ribs. Neither 

 do Branco's specimens seem to agree with one another. The specimen depicted in 

 figs. 2, 2a, is not only finer ribbed, but has a smaller umbilicus than fig. 1. The 

 specimen shown in fig. 3 certainly agrees more nearly with Dumortier's fig. 2 

 in side view, and yet it agrees rather better with certain fine-ribbed forms of 

 Dum. subundulata. As no front view is given this point must remain uncertain. 



It is necessary to restrict Branco's name " pseudoradiosum " to his fig. 1; 

 but unfortunately no front view of this specimen is given, and so I cannot be per- 

 fectly certain whether my identification be correct. 



The ribs of Dum. pseudoradiosa vary in their size and distance apart. At first 

 they are large and distant, then they are small and approximate, and finally they 

 are coarser and distant again. Branco noticed this fact (p. 77), and my speci- 

 mens both show a fine-ribbed period, though it is a very short one, succeeded by 

 a coarser-ribbed period. This character, however, is of little specific value, for it 

 is not confined to this species. As now defined, Dumortieria pseudoradiosa does 

 not differ very greatly from Dum. radians, especially from the south-country 

 specimens (p. 249). It is, however, of much coarser build altogether, and its 

 whorls are considerably thicker. Judging from the very depressed centre of 



