jb  YORKSHIRE TYPE AMMONITES Dec. 



3. AMMONITES AUREUS, Simpson 

 (Plate III) 



Original Description 

 " 34. A[mmonites] aureus. [M. Simpson, 1855, pp. 44, 45.] 



[" Without a dorsal keel or furrow. 

 " a. No spines." p. 35.] 



" Volutions 5, exposed, outer whorl J the diameter ; radii numerous, 

 straight, sharp, equaJ to the intervening concave spaces, ornamented 

 [p. 45] with two rows of flattened tubercles ; back rounded, nearly plane ; 

 aperture subquadrate ; diameter i inch. — L. L. ; R. H. Bay [Lower 

 Lias, Robin Hood's Bay]. 



"This resembles A. Ripleyi, but the outer whorl is narrower, and 

 the radii are much sharper, and more prominent, and have two rows 

 of tubercles ; the ramifications of the septa are very delicate, rounded, 

 and numerous." 



Additional Details 

 Simpson, 1884, p. 74, none ; p. xxi, entered in Lower Lias 13. 



Remarks 



Stages, conch, serpenticone ; periphery, i ; ornament 5**. 



The suture-lines are crowded, somewhat intricate, and difficult to 

 follow. They show a general likeness to the pattern of A. maugenesti 

 depicted by d'Orbigny, and also to that of A. regnardi, of the same author. 



The diameter of No. 107 is 27 mm. 



The genus is Platypleuroceras, Hyatt (Gen. p. 7), and family 

 Polymorphidae. 



If the genus is correct, then the geological position given by Simpson 

 is too low : it is probably from Lower Lias y instead. 



There is a prior Am. aureus, Young & Bird, 1822 ; but Si.mpson's 

 name is a homonym, not a synonym, so it can be retained. 



Result 

 Platypleuroceras aureum, Simpson sp. 1855 [Charmouthian, 

 about ■jamesoni-zone], Robin Hood's Bay, near Whitby. 



