358 8. 8. Buckman — On Jurassic Ammonites. 



Cymbites globosus (Zieten). 



1830. Ammonites globosus, Zieten, Verst. Wiirt. pi. 28, fig. 2. 



1849. Ammonites globosus, Quenstedt, Ceph. pi. 15, fig. 8. 



1853. Ammonites globosus, Oppel, Mittl. Lias Schwabens. pi. 3, fig. 7. 



1864. Amtnonites Icevigatus, Dumortier [^non Sowerby), Bass. Ehone, pi. 18, 



figs. 5 and 6. 

 1885. Ammonites globosus, Quenstedt, Schwabischen Amnion, (pi. 22, figs. 



45, 46?),i pi. 42, fig. 29 only. 

 1889. Agassiceras Icevigatum, Hyatt, Genesis Arietidae ; Smithsonian Contrib. 



Knowledge, 673, pi. vii. fig. 13 only. 



(But not Cymbites globosus, Geyei', Cepb. Hierlatz ; k.k. geol. Eeicbsanstalt, 

 Bd. xii. IS'o. 4, pi. iii. fig. 26, 1886.) 



An involute, smooth, globose sliell, always very small. There is 

 a tendency to enlarge the umbilicus in the last whorl, and to produce 

 an evolute shell. The septa are exceedingly simple for an Ammonite, 

 one two-pointed lobe on the periphery, and two simple lobes on 

 the side. 



There is but little difference apparently between the forms figured 

 from the angulatus-zone (Dumortier) and those from the margaritatus- 

 zone (Quenstedt). Some of the figures quoted in the above synonymy 

 are rather more widely centred than others ; and this, together with 

 the length of time above-noticed, makes it doubtful if they are 

 all the same species. As, however, the figures are small it is not 

 safe to pass a definite opinion on the subject one way or the other. 

 Enlarged figures of the forms from each horizon, all to the same 

 scale, are required. Further, it is necessary that the inner whorls 

 of species on the same horizons which might be mistaken for them 

 should be similarly figured. 



This species is quoted from the avguJatus-, Bucldandi-,'^ ohiusiis-,^ 

 oxynotus-, and margaritatus-zones. I can call to mind no other 

 Ammonite with anything like this range. 



Cymbites l^vigatus (Sowerby). 



1829, Ammonites Icevigatus, Sowerby {non Eeinecke), M. Conch, pi. 670, fig. 3- 



1849. Ammonites Daviclsoni, d'Orbigny, Prodi'ome i. p. 225, No. 38. 



1856. Ammonites Icevigatus, Oppel, Jurat, p. 81. 



1875. Agassiceras Icevigatum, Hjaii. Two new genera Ammonites ; Proc. Boston 



Nat. Hist. Soc. vol. 17, p. 226. 

 1887. Agassiceras Icevigatum, Haug, Polymorphidse ; N. Jahrbuch fiir Mineral, etc. 



Bd. ii. p. 94. 

 1889. Agassiceras Imvigatum, Hyatt, Genesis Arietidae ; Smithsonian Contrib. 



Knowledge, 673, pi. viii. fig. 12 (9, 11 ?). 



This species is thinner and more evolute than C. globosus ; and it 

 may be regarded as a development of that form having charac- 

 teristics which are due to the earlier inheritance of the adult features 

 of that one. Hyatt's figure 12 is typical; but his figs. 9, 11, are 

 developments of this species to the subcostate stage. They are 

 possibly connecting links ; thus his fig. 9 might lead to Agassiceras, 

 and his fig. 11 to something like planicosta. 



1 Probably young forms of oxynotus. 



~ These records may refer to Cymbites Icevigatus (Sow.). 



