27b YORKSHIRE TYPE AMMONITES Mar. 



27. AMMONITES OMISSUS, Simpson, 

 (Plate XXVII) 



Original Description 

 '' 44. A[mmonites] omissus. [M. Simpson, 1855, p. 47.] 



[" I. Without a dorsal keel or furrow. 

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



" Volutions 5, exposed, outer whorl more than -J the diameter ; 

 radii numerous, prominent sharp, sej^arated by concave spaces, suddenly 

 bend towards the aperture in passing over the back ; aperture roundish ; 

 diameter i and two tenths inch. 



" This may be distinguished from A. defossus by the inner whorls 

 being more slender and numerous, and by their having more numerous 

 and finer radii. It is from the same beds as the last [A. arcigerens. — 

 L.L. ; R. H. Bay]." 



Simpson, 1884, jj, the same. 



Remarks 



Stages, concn, serpenticjne ; periphery, i ; ornament, 4. 

 The outer whorl is less than J the diameter, which too is iy\j inch. 

 This is a species of Oistoceras{Ger\. p. iv) in the pre-tuberculate stage. 

 Geological position probably that of A. figulinus. 



Result 



OiSTOCERAS OMissuM, SiMPSON sp. 1855, Charmouthian [striatum- 

 zone], Robin Hood's Bay, near Whitby. 



