58b YORKSHIRE TYPE AMMONITES May 



58. AMMONITES CRASSULOSUS, Simpson 

 (Plate LVIII) 



Original Description 

 63. A[mmonites] crassulosus. [M. Simpson, 1855, p. 55.] 



[" 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.] 



" Thickish ; outer whorl less than \ the diameter ; radii smooth, 

 strong, prominent, distinct, separated by widish concave spaces, split in 

 two near the back, and bend towards the aperture ; aperture half of a 

 regular ellipse ; diameter 3 inches. 



" This differs chiefly from the communis or crassus type by the 

 prominence of the radii and their wider intervening spaces. The shell 

 is thick, and the whole form gives the idea of strength. The middle is 

 imperfect. It appears to be from the hard iron bands of the middle lias." 



Simpson, 1884, 86, 87, the same. 



Remarks 



Stages, conch, serpenticone ; periphery, i ; ornament, 4. 



Genus, presumably Dactylioceras, Hyatt (Gen. v) ', but uncertain 

 owing to absence of inner whorls ; family, Dactyloidse, Hyatt. Geological 

 position, " Middle Lias " (Simpson), presumably then, from the very top. 



Result 



Dactylioceras crassulosum, Simpson sp. 1855, Domerian, [acutnm 

 zone ? near Whitby]. 



