INFERIOR OOLITE OF DORSET AND SOMERSET. 



59 



Now as to the forms which, up to this time we have found with 

 terminations to their shells, we may state that as yet we have only 

 met with fourteen ; but it happens, as a rule, that the species so dis- 

 tinguished number several individuals, though some three or foui 

 of them have only yielded single specimens. 



Our list, then, includes the following species : — 



Terminations. 



J 1. Ammonites concavus, Sow. 



Lanceolate \ 2. subradiatus, Sow. 



[ 3. Edouardianus, I>' Orb. 



( 4. Braikenriclgii, Sow. 



Ovate-lanceolate I £ — ^f]?^ M ' 



or spathulate, ] ^ Martinsii, If Orb. 



\ 8. subcostatus, JBuchnan, MS. 



-pv i -i • i i f 9. Gervillii, Sow. 



Delphmulate, 1n -r, . ' . a 



r • • i i 10. TJroneniarti. bow. 



semicircular. -,, T- t> ' 7 



[11. Manseln, Buckman. 



I 1 2. Humpliriesianus. Sow. 



"Waved j 13. ■ Moorei, Lycett. 



| 14. ■ boscensis, Eegnes. 



Here, then, we have given fourteen species of Ammonites with 

 their terminations more or less complete ; and for these we have at- 

 tempted to make a provisional classification. 



So far as we have been enabled to examine these more complete 

 specimens of Ammonites, we arrive at the conclusion that, the 

 terminations to the shells are capable of greatly aiding in the 

 determining of species, as trimmed-up examples of A. linguiferus, 

 with their broadly oval or spathulate mouths, are difficult to distin- 

 guish from A. Humpliriesianus ; but when we have the semicircular 

 rugose mouth of the latter for comparison with the former the 

 difficulty vanishes. Thus, again, the lanceolate termination of the 

 discoid A. subradiatus is very different from the spathulate or ovato- 

 lanceolate ending of A. subcostatus (Buckm.) ; and yet these two forms 

 have been referred to one species by different authors. 



The dephinulate mouth in A. Gervillii is a complicated ter- 

 mination when compared with the plainer semicircular terminations 

 of A. Brongniarti and A. Humpliriesianus ; and yet without this 

 knowledge we had always confounded the first two forms. 



Erom these remarks it seems but reasonable to conclude that the 

 terminations of Ammonites may become important in the distinguish- 

 ing of species, though, from what we have seen, their preservation is 

 of somewhat rare occurrence ; at the same time our own experience 

 seems to point to the fact that many fine examples of more com- 

 plete shells have been lost from the want of due observation upon 

 the subject. We may further mention that, with the vast numbers 

 of Cephalopada which are everywhere around us and which are so 

 perfect in other respects, we have not yet seen a single example either 

 of Mhyncholites or Trigonellites. Mr. S. P. Woodward, however, has 

 figured an Ammonite with the operculum from Dundry*. The shell 

 * See 4 Geologist,' vol. iii. p. 328. 



