598 



S. S. BTTCKMAN ON AMMONITES FROM 



This species, when young, is extremely like Splicer. Brongniarti 

 (Sow.), plate 184 a. fig. 2, but when larger is easily distinguished 

 by its very fine and numerous bifurcating ribs and its very square 

 ventral area, especially just by the termination, and its far greater 

 breadth. It also attains a larger size than Splicer. Brongniarti. The 

 termination is also peculiar — first a small lip, then a deep furrow, 

 then another lip and band. 



This species was named but not figured by Mr. J. Buckman in 

 his paper read before the Geological Society. 



Dimensions. Diameter 1*75 inch; umbilicus 0*33; aperture 

 across 1*20 ; aperture back to front 0*45. 



Locality. Clatcombe, near Sherborne. Two fine specimens were 

 obtained from this place by T. C. Maggs, Esq. I do not know of 

 any other specimens. 



Sph^koceras polymorphtjm (d'Orb.). 



1845. Ammonites polymorphus, d'Orb. Terr. Jurass. pi. 124. figs. 

 1,2, 3, 4, 5? 6? 



1849. A. ParJcinsoni inflatus, Quenstedt, Ceph. Tab. ii. figs. 

 6 and 7. 



1854. A. polymorplius (d'Orb.), Morris, Catalogue, p. 294. 



1856. A. polymorphic (d'Orb,), Oppel, Juraform. p. 382. 



"We have undoubtedly found in this neighbourhood specimens 

 which exactly correspond with those figured by d'Orbigny, 4 Ter- 

 rains Jurassiques,' pi. 124. figs. 1, 2, 3, 4 ; but we have not found 

 any to correspond with figs. 5 and 6 ; and I have my doubts about 

 figs. 5 and 6 really being the adult form of the others. Oppel, too, 

 in quoting A. polymorplius, d'Orb., leaves out nos. 5 and 6 (see 

 Oppel, 4 Juraformation,' p. 382, no. 54). 



Localities. Zone of Cosmoceras ParJcinsoni at Broad Windsor, Bur- 

 ton Bradstock, and other places. 



Sph^roceras dimorphum (d'Orb.). 



1845. Ammonites dimorphus, d'Orb. Terr. Jurass. pi. 141. 



1854. A. dimorphus (d'Orb.), Morris, Catalogue, p. 291. 



This species varies somewhat in the width of its umbilicus. Some 

 specimens have the umbilicus nearly closed, while others of the same 

 size have the umbilicus much larger, so that a portion of the 

 inner whorls can be seen. 



In the adult form the umbilicus widens rather quickly, as is 

 well shown by d'Orbigny, pi. 141. fig. 1. 



The variety represented by d'Orbigny (pi. 141. figs. 3 and 4) 

 has, so far as I know, not yet been obtained from this district. 



I possess only one specimen with the termination. It is a 

 form with a rather wide umbilicus. The termination is merely 

 a small furrow and a semilunar lip beyond. The specimen came 

 from Bradford Abbas. 



Localities. Zone of Cosmoceras ParJcinsoni at Halfway House, 

 Broad Windsor, Stoford, and other places. 



