68b 



YORKSHIRE TYPE AMMONITES-II May 



68. AMMONITES VERMIS, Simpson 

 (Plate LXVIII) 



Original Description 

 " 55. A[mmonites] vermis. [M. Simpson, 1855, p. 51J 



[" The following species, to the end of the Section, have all a family 

 resemblance to A. communis : — 



" Whorls narrow, exposed, with numerous slender, annular ribs, 

 which generally split in two on the back." p. 50.] 



" Volutions slender ; radii nearly obsolete on the outer whorl ; 

 aperture nearly round. — Jet-rock." 

 Simpson, 1884, 82, the same. 



Remarks 



Proportions, 30, 22, 22, 55 : Substeno-, subleptogyral, sub- 

 ext remilat umbilicat e . 



Stages, conch, serpenticone ; periphery, 1; ornament, 4 (4c?). 



Umbilicus open, flat ; inclusion very little ; ribs numerous, feeble, 

 bifurcate on edge of a slightly arched periphery. The periphery is much 

 worn. There are no tubercles visible at points of bifurcation. 



Genus, Dactylioceras, Hyatt ; family, Dactyloidae, Hyatt. 



This is a noticeable little species, because from the peripheral position 

 of the bifurcation a side view shews merely single primary ribs. 



Result 



Dactylioceras vermis, Simpson sp. 1855, Whitbian, exaratum 

 zone, [near Whitby]. 



