288 ME. s. s. BUCKMAN OjS" [vol. Ixxiii, 



falls somewhat steeply to the umbilicus ; excentrumbilication is 

 apparent in the last half- whorl (beyond the part preserved) — the 

 OA^erlap decreasing from about four-fifths to tAVO-thirds. 



Remarks. — In ornament, peripher}^ and general appearance 

 the species here described conforms with Ammonites huvigneri 

 Dumortier ; but it differs in having a larger umbilicus with a much 

 steeper border and a thinner whorl the greatest thickness of which 

 is not on the edge of the umbilical border but well removed from it. 



Ammonites huvigneri D'Orbigny is a much thinner species than 

 Dumortier's, and has passed beyond the costate stage. Its um- 

 bilicus is much smaller than the Radstock species ; its suture-line 

 shows the general pattern thereof, but is not truly conformable m 

 many respects : it does not seem so highly developed : the lobules 

 which penetrate the external saddle are much less developed and 

 different — the first lobule is long and bipartite in the Radstock 

 species, short and simple in D'Orbigny's ; the superior lateral lobe 

 has its outer lobule bipartite in the Radstock example, its inner 

 one is so in D'Orbigny's : in the former the terminal lobule has its 

 shortest side internal (endobrachysceles), in the latter external 

 (ectobrachysceles).i The specimens figured by Dumortier and 

 D'Orbigny are both separable from the Radstock species by greater 

 occlusion — they are perangustumbilicate. Pompeckj says that 

 these two ought to be considered as the same species : ^ I differ. 



Phylloceras huvigneri Wright is also a perangustumbilicate 

 oxycone. comparable as regards sculpture with D'Orbigny's species, 

 but wholly different in whorl-shape and in suture-line. It looks 

 as if all these oxynotes are homoeomorphous terminals of different 

 lineages — their polygenetic origin shown by the different character 

 which each selects for acceleration — in one case suture-line, in 

 another, ornament, in another, inclusion, in another, whorl-shape. 

 Considerable inequality of characters is thus produced. 



For references and proportions see Table XIII, below. 



History of figured specimen. — From Radstock Grove 

 (Kilmersdon Colliery), Radstock, Somerset, [from beds yielding 

 Oxynotoids immediately below the so-called ^ raricostatus beds ']. 

 Purchased. See p. 310. 



Table XIII. — Proportions : Badsiockicjeras and like Forms. 



Radstockiceras compUcatum nov. 



S. 186, 

 S. 262, 





54, 

 55, 



25, 

 25, 



11. 

 11. 



Ammonites huvigneri D'Orbigny^. 



F.200 

 T.200, 



(93), 



56, 

 58, 



21, 

 21, 



4. 

 4. 



Ammonites huvigneri Dumortier"'. 



T.126, 





58, 



28, 



4. 



Phylloceras huvigneri (Wright), 

 Ixxvi, 1, 25 



F.150, 

 T.145, 





54, 

 56, 



30, 

 32, 



7. 





4. 



^ ' Monogr. Inf. Oolite Ammonites ' p. 381. 



- 'Oxynot. Sinem.' Comm. Serv. Geol. Port, vi (1906) p. 270. 



■' ' Pal. franc;. : Terr. Jnr. Ceph.' 1844, pi. Ixsiv & p. 261. 



^ ' Bassin Ehone ' ii (1867) pi. xxxiv, p. 147. 



'° 'Monogr. Lias Ammonites ' (Pal. Soc). 



