65b YORKSHIRE TYPE AMMONITES Oct. 



65. AMMONITES OWENENSIS, Simpson 

 (Plate LXV) 



Original Description 

 " 41. A[mmonites] Owenensis. [M. Simpson, 1843. pp. 25, 26.] 



["I. Without a dorsal keel or. furrow, p. 7. 

 " b. Armed with spines or distinct tubercles." p. 22.] 



" Depressed ; Volutions 5 or 6, exposed, outer whorl more than 

 ^ the diameter ; radii rather distant, straight, distinct, slender, armed 

 with a row of tubercles near the outer margin, obsolete on the back, 

 and on the inner whorls ; aperture round ; diameter i inch. 



" In the form of the whorls this species resembles A. fimbriatus, 

 and the size of the aperture is comparatively much greater than [p. 26] 

 in any other of the armed varieties. The cast is smooth and without 

 any appearance of striae ; I suppose it to be from the lower lias ; but on 

 this I am not able to speak with certainty. 



" I have taken the liberty of naming this ammonite after Professor 

 Owen, whose works on Saurians, and whose talents as a naturalist have 

 placed him far above any praise that can be given him here." 



Additional Details 



Simpson, 1855, 64, omits " Depressed " ; has instead of 2nd and 

 3rd paragraphs " The whorls diminish rather rapidly ; and in some 

 specimens the radii are very distant. The cast is very smooth and 

 neat.— L.L. ; R. H. Bay." 



Simpson, 1884, 64, as 1855. 



Remarks 



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



Whorls obtrapeziform ; sides divergent, flattened ; periphery flatly 

 arched, faintly lineate (striate) ; greatest thickness at edge of periphery, 

 where there is a coronet of spines. Smooth stage to about 12 mm. 

 diameter, then distant, not strong costae, each ending in a spine. 



The specimen is quite immature. 



Genus, Deroceras, Hyatt, 1867 ; family, Deroceratidae, Hyatt. The 

 geological j)osition is presumably L.L.y. 



Result 



Deroceras owenense, Simpson sp. 1843, Charmouthian, [armatum 

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



