38b YORKSHIRE TYPE AMMONITES Nov. 



38. AMMONITES SULCATUS, Simpson 

 (Plate XXXVIII) 



Original Description 

 " 108. A[mmonite.s] sulcatus. | M. Simpson, 1843, pp. 55, 56.] 



[" IV. With a dorsal furrow only." p. 55] 



" Depressed ; volutions much concealed, outer whorl nearly J the 

 diameter ; radii strong on the inner margin of the whorl, then split in 

 two or three, [p. 56] faint, twice bent ; an angular furrow on the back ; 

 ajjerture triangular ; diameter | inch. 



" This interesting little ammonite may be readily distinguished 

 from the rest, by the angular furrow on the back ; which is very distinct 

 on the outer whorls, and becomes a mere line on the inner ones. It like 

 a great many other small and beautiful species is from the lowest beds 

 of lias at Robin Hood's Bay." 



Simpson, 1855, loi ; 1884, 142, the same. 



Remarks 



Stages, conch, serpenticone ; periphery, sulcate ; ornament, 3c. 



The diameter is really | inch (16 mm.). The radii are well flexed. 

 The specimen is worn. 



Genus, Schlotheimia, Bayle, 1878. Geological position about L.L. 16, 

 or higher. 



Ihe name antedates A. sulcatus, J. Huckman, by a year : the latter 

 may therefore become Schlotheimia sulcifera (see Pal. U. 1904, 39, T2). 



Result 



Schlotheimia sulcata, Sfmpson sp. 1843, Sinemurian [slellare- 

 oxynotum zone], near Whitby. 



