igocj AMMONITES DENNY I 7c 



all up to 5t and 4c. Pompeckj has noted the presence of auriculoids 

 in certain Oxynoticeras species (p. 274). Thus A. dennyi, with its auricu- 

 loid, is not a primitive form, but a decadent — a post-auritulum, pre- 

 oxynotum Oxynoticeras, Hyatt (Gen. p. H) ; and its contracted body- 

 chamber is not a gerontic sign : it is normal growth from sphaerocone 

 towards oxycone. 



The retention of the goniatitic form until the advent of the auriculoid 

 is a case of undue prolongation or retention of larval characters : it is 

 cunctative palingenesis. The jump from stage i to stage 5 is an example 

 of saltative palingenesis ; and the appearance of the auriculoid before 

 the carina is an instance of precedentive pahngenesis. 



Result 



O.WNOTiCERAs DENNYI, SiMPSON, sp. 1843, Sincmurian, oxynotum- 

 zone, Robin Hood's Bay, near Whitby. 



Comparable Species 

 Am. auritulas, Quenstedt (non A. riparius, Oj^pel), Am. Schwab. 

 Jura, 1884, PI. XXIV, fig. 13 only. Take this as type of A. auritulus. 

 Oxynoticeras oxynotum ; Hyatt, i88q, x, 4, 5, 14 — 20. 



