47 



circumstances it is deemed advisable to keep the two species separate, 

 at least for the present, and a provisional name has been suggested, 

 accordingly, for the fossil collected by Mr. Eichardson. 



Group 8. — Doubtful Species. 

 Ammonites (Sp. undt.) 



Plate III., figures 4, 4a. 



Compare A. simplus D'Orbigny. 



" Paleoutologie Frau^aise. Terrains Cretaces." Vol. I., pages 208-9. Atlas, Vol. I., 

 Plate LX., figs. 7—9. 



Shell strongly involute, globose, the thickness being about a fifth 

 less than the greatest diameter ; umbilicus small but deep ; periphery 

 I'ounded ; aperture much wider than high. Surface nearly smooth, 

 marked only by a few lines of growth. 



Se^itation unknown. 



Diameter of the only specimen five lines; maximum thickness about 

 four lines; width of umbilicus rather less than one line. 



This little shell can scarcel}' be distinguished from the A. simplus of 

 D'Orbigny, as figured and described in the work just quoted. On the 

 other hand, many Ammonites have a globose, nautiliform shell in their 

 very j^oung state, so that this fossil is probably only an early stage of 

 growth of one of the species previously described, though, owing to the 

 want of a series of specimens of all ages, it is at present impossible to 

 say of which. 



Not a little difference of opinion exists as to what are the true 

 relations of D'Orbigny's A. simplus, which is generally believed to be the 

 young of some other species. D'Orbigny himself has united it with his 

 'A. verrucosus, a decision in which he has been followed by manj^ palae- 

 ontologists. Stoliczka disputes the correctness of this view, and with 

 much apparent justice. In the "Index Palaontologicus," (Yol. I., pages 

 49 and 50.) Bronn places A. simplus, though with a note of interrogation, 

 (implj'ing a doubt as to the propriety of the reference) among the 

 sj^ionj^ms of A. macrocephalus, Schlotheim. This suggests the idea that 

 the present shell may be the young of A. Loganiamis, nobis. Zittel 

 includes A. simplus in his genus Aspidoceras, and the fossil just described 

 is certainly very like the early stage of Oppel's A. cyclotum. As the 

 Ammonites Stoliczkanus of Gabb has many of the characters of Aspido- 

 ceras, this little shell may be the young of it. 



